c primer plus 11 编程练习

1、

#include <stdio.h>

#define SIZE 100

void get_n(char * ar, int n);

int main(void)
{
    int n;
    printf("n = "); scanf("%d", &n);
    
    while(getchar() != '
')
        continue;
    
    char st1[SIZE];
    
    get_n(st1, n);
    
    
    puts(st1);
    int i;
    for(i = 0; i < n; i++)
    {
        printf("st1[%d]: %c
", i, st1[i]);
    }

    return 0;
}

void get_n(char * ar, int n)
{
    int i;
    
    puts("please input the elements of the strings.");
    for(i = 0; i < n; i++)
    {
        scanf("%c", &ar[i]);
    }
    
}

#include <stdio.h>
#define SIZE 40

char * read_char(char *st, int n);

int main(void)
{
    char test[SIZE];
    puts("Start to test function, enter a string.");
    
    read_char(test, 5);
    
    puts("The string you input is: ");
    puts(test);
    
    return 0;
}

char * read_char(char *st, int n)
{
    int i = 0;
    do
    {
        st[i] = getchar();
    }
    while(st[i] != EOF && ++i < n);
    
    return 0;
}

2、

#include <stdio.h>
#define SIZE 40

char * read_char(char *st, int n);

int main(void)
{
    char test[SIZE];
    
    puts("Start to test function, enter a string.");
    read_char(test, 5);
    
    puts("The string you input is：");
    puts(test);
    
    return 0;
}

char * read_char(char *st, int n)
{
    int i = 0;
    
    do
    {
        st[i] = getchar();
        if(st[i] == '
' || st[i] == '	' || st[i] == ' ')
            break;
    }
    while(st[i] != EOF && ++i < n);
    
    return st;
}

3、

#include <stdio.h>

#define SIZE 100

char * get_word(char *st, int n);

int main(void)
{
    char word[SIZE];
    char * temp;
    
    temp = get_word(word, SIZE);
    
    puts(temp);
    
    return 0;    
} 

char * get_word(char *st, int n)
{
    char * temp;
    int i = 0;
    
    temp = fgets(st, n, stdin);

    if(temp)
    {
        if(st[0] == ' ')
        {
            while(st[i] == ' ')
                i++;
        }
    }
    
    temp += i;
    
    while(st[i] != ' ' && st[i] != '	' && st[i] != '
')
        i++;
    
    st[i] = '';
    
    return temp;
}

#include <stdio.h>

#define SIZE 100

char * get_word(char *st, int n);

int main(void)
{
    char word[SIZE];
    char * temp;
    
    temp = get_word(word, SIZE);
    
    puts(temp);
    
    return 0;    
} 

char * get_word(char *st, int n)
{
    char * temp;
    int i = 0;
    
    temp = fgets(st, n, stdin);

    if(temp)
    {
        if(st[0] == ' ')
        {
            while(st[i] == ' ')
                i++;
        }
    }
    
    temp += i;
    
    while(st[i] != ' ' && st[i] != '	' && st[i] != '
')
        i++;
    
    if(st[i] == ' ' || st[i] == '	' || st[i] == '
')
        st[i] = '';
    else
        while(getchar() != '
')
            continue;
            
    return temp;
}

#include <stdio.h>
#include <ctype.h>

#define SIZE 80

char * get_word(char *out);

int main(void)
{
    char output[SIZE];
    get_word(output);
    
    printf("the first word you input is: %s", output);
    
    return 0;
}

char * get_word(char *out)
{
    char input[SIZE];
    char *in = input;
    
    puts("enter a string: ");
    fgets(input, SIZE, stdin);
    
    while((*in == '
' || *in == '	' || *in == ' ') && *in != '')
        in++;
    
    while(*in != '
' && *in != '	' && *in != ' ' && *in != '')
        *out++ = *in++;
    
    return out;
}

#include <stdio.h>

#define SIZE 100

char * get_word(char *st, int n);
int main(void)
{
    char word[SIZE];
    char *tmp;
    
    tmp = get_word(word, SIZE);
    
    puts(tmp);
    
    return 0;
}

char * get_word(char *st, int n)
{
    char *tmp;
    int i = 0;
    
    tmp = fgets(st, n, stdin);
    
    if(tmp)
    {
        while((st[i] == ' ' || st[i] == '	' || st[i] == '
') && st[i] != '')
            i++;
        
        tmp += i;
        
        while(st[i] != ' ' && st[i] != '	' && st[i] != '
' && st[i] != '' )
            i++;
        
        if(st[i] == ' ' || st[i] == '	' || st[i] == '
')
            st[i] = '';
        else
            while(getchar() != '
')
                continue;    
    }
    
    return tmp;
}

#include <stdio.h>

#define SIZE 100

char * get_word(char *st, int n);

int main(void)
{
    char st1[SIZE];
    char * fword;
    
    printf("please input the strings.
");
    
    fword = get_word(st1, SIZE);
    
    printf("first word: %s
", fword);
    
    return 0;
}

char * get_word(char *st, int n)
{
    char * temp;
    int i = 0;
    
    temp = fgets(st, n, stdin);
    
    if(temp)
    {
        while((st[i] == ' ' || st[i] == '	' || st[i] == '
') && st[i] != '')
            i++;
        
        temp += i;
        
        while(st[i] != ' ' && st[i] != '	' && st[i] != '
' && st[i] != '')
            i++;
        
        if(st[i] == ' ' || st[i] == '	' || st[i] == '
')
            st[i] = '';
        else
            while(getchar() != '
')
                continue;
    }
    
    return temp;
}

4、

#include <stdio.h>

#define SIZE 100

char * get_word(char *st, int n);

int main(void)
{
    char st1[SIZE];
    char * fword;
    
    printf("please input the strings.
");
    
    fword = get_word(st1, SIZE);
    
    printf("first word: %s
", fword);
    
    return 0;
}

char * get_word(char *st, int n)
{
    char * temp;
    int i = 0;
    
    temp = fgets(st, n, stdin);
    
    if(temp)
    {
        while((st[i] == ' ' || st[i] == '	' || st[i] == '
') && st[i] != '')
            i++;
        
        temp += i;
        
        while(st[i] != ' ' && st[i] != '	' && st[i] != '
' && st[i] != '')
            i++;
        
        if(st[i] == ' ' || st[i] == '	' || st[i] == '
')
            st[i] = '';
        else
            while(getchar() != '
')
                continue;
    }
    
    return temp;
}

5、

#include <stdio.h>

#define SIZE 100

char * search_ch(char * ar, char ch);
char * s_gets(char *st, int n);


int main(void)
{
    char st1[SIZE];
    char * find;
    char ch;
    char xx;
    
    do
    {
        puts("input the string: ");
        s_gets(st1, SIZE);
        
        printf("please input the ch: "); scanf("%c", &ch); 
        find = search_ch(st1, ch);
        if(find)
            puts(find);
        else
            puts("nothing found!");
        
        while(getchar() != '
')
            continue;    
        printf("quit(q to quit!); other continue xx: "); scanf("%c", &xx);
        while(getchar() != '
')
            continue;
    }
    while(xx != 'q');
    
    return 0;
}

char * search_ch(char * ar, char ch)
{
    int i = 0;
    char * find;
    
    while(ar[i] != ch && ar[i] != '')
        i++;
    
    if(ar[i] == ch)
        find = ar + i;
    else
        find = NULL;
        
    return find;
}

char *s_gets(char *st, int n)
{
    char * ret_val;
    int i = 0;
    
    ret_val = fgets(st, n, stdin);
    
    if(ret_val)
    {
        while(st[i] != '
' && st[i] != '')
            i++;
        
        if(st[i] == '
')
            st[i] = '';
        else
            while(getchar() != '
')
                continue;
    }
    return ret_val;
}

#include <stdio.h>

#define SIZE 81

char * get_pos(char *st, char ch);

int main(void)
{
    char st1[SIZE];
    printf("st1: 
");
    fgets(st1, SIZE, stdin);
    char des = ' ';
    char *pos;
    
    printf("please input the dest.
");
    
    while(des != EOF)
    {    
        printf("intput a ch or EOF to quit
");
        while((des = getchar()) == '
')
            continue;
        
        if((pos = get_pos(st1, des)) != NULL)
            printf("%c first in %p
", *pos, pos);
        
        else
            printf("nothing fonud.
");
        printf("go on or quit?"); 
        
    }
    return 0;
}

char * get_pos(char *st, char ch)
{
    while(*st != '')
    {
        if(*st == ch)
            return st;
        else
            st++;
    }
    return NULL;
}

6、

#include <stdio.h>

#define SIZE 100

int find_ch(char ch, char * ar);

int main(void)
{
    char st1[SIZE];
    char target;
    
    printf("please iput the strings: ");
    fgets(st1, SIZE, stdin);
        
    while(1)
    {
        printf("please input target character(EOF to quit): ");
        target = getchar();
        
        if(target == EOF)
            break;
            
        while(getchar() != '
')
            continue;
            
        if(find_ch(target, st1) != 0)
        {
            printf("find the target!

");
        }
        else
        {
            printf("not fond the target!

");
        }
        puts("go on or quit? ");
    }
}

int find_ch(char ch, char * ar)
{
    while(*ar != '')
    {
        if(*ar == ch)
            return 1;
        else
            ar++;
    }
    return 0;
}

6、

#include <stdio.h>

#define SIZE 100

char * s_gets(char *st, int n);
int find(char ch, char *ar);

int main(void)
{
    char st1[SIZE];
    puts("please input the strings.");
    s_gets(st1, SIZE);
    char target;
    
    while(1)
    {
        printf("please input the target character(EOF to quit).
");
        target = getchar();
        
        if(target == EOF)
            break;
        
        while(getchar() != '
')
            continue;
        
        if(find(target, st1) != 0)
        {
            puts("find the target!
");    
        } 
        else
        {
            puts("not find the target!
");
        }
        puts("go on or quit? ");
    }
    
        
}

int find(char ch, char *ar)
{
    while(*ar)
    {
        if(*ar == ch)
            return 1;
        else
            ar++;
    }
    return 0;
}


char * s_gets(char *st, int n)
{
    char * ret_val;
    int i = 0;
    
    ret_val = fgets(st, n, stdin);
    
    if(ret_val)
    {
        while(st[i] != '
' && st[i] != '')
            i++;
        
        if(st[i] == '
')
            st[i] = '';
        else
            while(getchar() != '
')
                continue;
    }
    return ret_val;
}

7、

#include <stdio.h>

#define SIZE 80

char * mystrncpy(char * ar1, char * ar2, int n);
char *s_gets(char *st, int n);

int main(void)
{
    char st1[SIZE];
    char st2[SIZE];
    
    printf("input source string: ");
    s_gets(st2, SIZE);
    int num;
    printf("input  copy  number: "); scanf("%d", &num);
    
    mystrncpy(st1, st2, num);
    printf("string copy  result: %s
", st1);
    
    return 0;
}

char * mystrncpy(char * ar1, char * ar2, int n)
{
    int i = 0;
    
    while(i < n &&  ar2[i] != '')
    {
        ar1[i] = ar2[i];
        i++;
    }
    
    if(i < n)
    {
        while(i < n)
        {
            ar1[i] = '';
            i++;
        }
    }
    
    return ar1;
}

char *s_gets(char *st, int n)
{
    char * ret_val;
    int i = 0;
    
    ret_val = fgets(st, n, stdin);
    
    if(ret_val)
    {
        while(st[i] != '
' && st[i] != '')
            i++;
        
        if(st[i] == '
')
            st[i] = '';
        else
            while(getchar() != '
')
                continue;
    }
    return ret_val;
}

循环：

#include <stdio.h>
#include <string.h>

#define SIZE 80

char * mystrncpy(char * ar1, char * ar2, int n);
char *s_gets(char *st, int n);

int main(void)
{
    char st1[SIZE];
    char st2[SIZE];
    
    while(1)
    {
        printf("input source string(q to quit): ");
        s_gets(st2, SIZE);
        if(strcmp(st2, "q") == 0)
            break;
        int num;
        printf("input  copy  number: "); scanf("%d", &num);
        
        mystrncpy(st1, st2, num);
        printf("string copy  result: %s
", st1);
        
        while(getchar() != '
')
            continue;
    }
    
    return 0;
}

char * mystrncpy(char * ar1, char * ar2, int n)
{
    int i = 0;
    
    while(i < n &&  ar2[i] != '')
    {
        ar1[i] = ar2[i];
        i++;
    }
    
    if(i < n)
    {
        while(i < n)
        {
            ar1[i] = '';
            i++;
        }
    }
    
    return ar1;
}

char *s_gets(char *st, int n)
{
    char * ret_val;
    int i = 0;
    
    ret_val = fgets(st, n, stdin);
    
    if(ret_val)
    {
        while(st[i] != '
' && st[i] != '')
            i++;
        
        if(st[i] == '
')
            st[i] = '';
        else
            while(getchar() != '
')
                continue;
    }
    return ret_val;
}

#include <stdio.h>
#include <string.h>

#define SIZE 80

char * mystrncpy(char * ar1, char * ar2, int n);
char *s_gets(char *st, int n);

int main(void)
{
    char st1[SIZE];
    char st2[SIZE];
    char ch;
    
    while(1)
    {
        printf("input source string(EOF to quit): ");
        if((ch = getchar()) == EOF)
            break;
            
        s_gets(st2, SIZE);
        int num;
        printf("input  copy  number: "); scanf("%d", &num);
        
        mystrncpy(st1, st2, num);
        printf("string copy  result: %s
", st1);
        
        while(getchar() != '
')
            continue;
    }
    
    return 0;
}

char * mystrncpy(char * ar1, char * ar2, int n)
{
    int i = 0;
    
    while(i < n &&  ar2[i] != '')
    {
        ar1[i] = ar2[i];
        i++;
    }
    
    if(i < n)
    {
        while(i < n)
        {
            ar1[i] = '';
            i++;
        }
    }
    
    return ar1;
}

char *s_gets(char *st, int n)
{
    char * ret_val;
    int i = 0;
    
    ret_val = fgets(st, n, stdin);
    
    if(ret_val)
    {
        while(st[i] != '
' && st[i] != '')
            i++;
        
        if(st[i] == '
')
            st[i] = '';
        else
            while(getchar() != '
')
                continue;
    }
    return ret_val;
}

8、

#include <stdio.h>

#define SIZE 80

char *s_gets(char *st, int n);
char *scan(char *ar1, char *ar2);

int main(void)
{
    char st1[SIZE];
    char st2[SIZE];
    printf("st1: "); s_gets(st1, SIZE);
    printf("st2: "); s_gets(st2, SIZE);
    char * scan_re;
    
    scan_re = scan(st1, st2);
    if(scan_re)
    {
        puts("
overlapping!");
        puts(scan_re);
    }
    else
        puts("
not overlapping!");
        
    return 0;
}

char *scan(char *ar1, char *ar2)
{
    int i = 0;
    while(ar1[i] != '')
    {
        if(ar1[i] == ar2[0])
        {
            int j = 0;
            while(ar1[i + j] == ar2[j] && ar2[j] != '')
                j++;
            if(ar2[j] == '')
                return ar1;
        }
        i++;
    }
    return NULL;
}


char *s_gets(char *st, int n)
{
    char *ret_val;
    int i = 0;
    
    ret_val = fgets(st, n, stdin);
    
    if(ret_val)
    {
        while(st[i] != '
' && st[i] != '')
            i++;
        
        if(st[i] == '
')
            st[i] = '';
        else
            while(getchar() != '
')
                continue;
    }
    return ret_val;
}

#include <stdio.h>

#define SIZE 100

char * s_gets(char *st, int n);
char *scan(char *ar1, char *ar2);

int main(void)
{
    char st1[SIZE];
    char st2[SIZE];
    char * scan_re;
    
    printf("please input st1: "); s_gets(st1, SIZE);
    printf("please input st2: "); s_gets(st2, SIZE);
    scan_re = scan(st1, st2);
    
    if(scan_re)
    {
        puts("overlapping!");
        puts(scan_re);
    }
    else
    {
        puts("not overlapping!");
    }
    
    return 0;
} 

char *scan(char *ar1, char *ar2)
{
    int i = 0;
    
    while(ar1[i] != '')
    {
        if(ar1[i] == ar2[0])
        {
            int j = 0;
            while(ar1[i + j] == ar2[j] && ar2[j] != '')
                j++;
            if(ar2[j] == '')
                return ar1 + i;
        }
        i++;
    }
    return NULL;
}

char * s_gets(char *st, int n)
{
    char *ret_val;
    int i = 0;
    
    ret_val = fgets(st, n, stdin);
    
    if(ret_val)
    {
        while(st[i] != '
' && st[i] != '')
            i++;
        
        if(st[i] == '
')
            st[i] = '';
        else
            while(getchar() != '
')
                continue;
    }
    return ret_val;
}

#include <stdio.h>

#define SIZE 100

char * s_gets(char *st, int n);
char *scan(char *ar1, char *ar2);

int main(void)
{
    char st1[SIZE];
    char st2[SIZE];
    char * scan_re;
    char temp;
    
    while(1)
    {
        
        printf("please input st1: ");
        s_gets(st1, SIZE);
        
        printf("please input st2: "); s_gets(st2, SIZE);
        scan_re = scan(st1, st2);
        
        if(scan_re)
        {
            puts("overlapping!
");
            puts(scan_re);
        }
        else
        {
            puts("not overlapping!
");
        }
        printf("y continue or EOF to quit): ");
        if((temp = getchar()) == EOF)
            break;
        else
            while(getchar() != '
')
                continue;
    }
    return 0;
} 

char *scan(char *ar1, char *ar2)
{
    int i = 0;
    
    while(ar1[i] != '')
    {
        if(ar1[i] == ar2[0])
        {
            int j = 0;
            while(ar1[i + j] == ar2[j] && ar2[j] != '')
                j++;
            if(ar2[j] == '')
                return ar1 + i;
        }
        i++;
    }
    return NULL;
}

char * s_gets(char *st, int n)
{
    char *ret_val;
    int i = 0;
    
    ret_val = fgets(st, n, stdin);
    
    if(ret_val)
    {
        while(st[i] != '
' && st[i] != '')
            i++;
        
        if(st[i] == '
')
            st[i] = '';
        else
            while(getchar() != '
')
                continue;
    }
    return ret_val;
}

#include <stdio.h>
#include <string.h>

#define SIZE 100

char * scan(char *ar1, char *ar2);
char * s_gets(char *st, int n);

int main(void)
{
    char ar1[SIZE];
    char ar2[SIZE];
    char * result;
    
    printf("ar1: "); s_gets(ar1, SIZE);
    printf("ar2: "); s_gets(ar2, SIZE);
    
     while(*ar1 != '
')
     {
         result = scan(ar1, ar2);
         
         if(result)
         {
             puts("overlapping!"); 
             printf("result: %p
", result);    
             printf("result: %s
", result);
        }
        else
        {
            puts("not overlapping!");
        }
        printf("ar1(blank to quit): "); s_gets(ar1, SIZE);

        if(ar1[0] == '')
            break;
        printf("ar2: "); s_gets(ar2, SIZE);
     }
     
     return 0;
}

char *scan(char *ar1, char *ar2)
{
    int count = 0;
    int ar2_len = strlen(ar2);
    
    while(*ar1 != '' && count < ar2_len)
    {
        if(*(ar1 + count) == *(ar2 + count))
        {
            count++;
        }
        else
        {
            count = 0;
            ar1++;
        }
    }
    if(count == ar2_len)
    {
        return ar1;
    }
    else
        return NULL;
}

char *s_gets(char *st, int n)
{
    char * ret_val;
    int i = 0;
    
    ret_val = fgets(st, n, stdin);
    
    if(ret_val)
    {
        while(st[i] != '
' && st[i] != '')
            i++;
        
        if(st[i] == '
')
            st[i] = '';
        else
            while(getchar() != '
')
                continue;
    }
    return ret_val;
}

#include <stdio.h>
#include <string.h>

#define SIZE 100

char * scan(char *ar1, char *ar2);
char * s_gets(char *st, int n);

int main(void)
{
    char ar1[SIZE];
    char ar2[SIZE];
    char * result;
    
    printf("ar1: "); s_gets(ar1, SIZE);
    printf("ar2: "); s_gets(ar2, SIZE);
    
     while(*ar1 != '')
     {
         result = scan(ar1, ar2);
         
         if(result)
         {
             puts("overlapping!"); 
             printf("result: %p
", result);    
             printf("result: %s
", result);
        }
        else
        {
            puts("not overlapping!");
        }
        printf("ar1(blank to quit): "); s_gets(ar1, SIZE);

        if(ar1[0] == '')
            break;
        printf("ar2: "); s_gets(ar2, SIZE);
     }
     
     return 0;
}

char *scan(char *ar1, char *ar2)
{
    int count = 0;
    int ar2_len = strlen(ar2);
    
    while(*ar1 != '' && count < ar2_len)
    {
        if(*(ar1 + count) == *(ar2 + count))
        {
            count++;
        }
        else
        {
            count = 0;
            ar1++;
        }
    }
    if(count == ar2_len)
    {
        return ar1;
    }
    else
        return NULL;
}

char *s_gets(char *st, int n)
{
    char * ret_val;
    int i = 0;
    
    ret_val = fgets(st, n, stdin);
    
    if(ret_val)
    {
        while(st[i] != '
' && st[i] != '')
            i++;
        
        if(st[i] == '
')
            st[i] = '';
        else
            while(getchar() != '
')
                continue;
    }
    return ret_val;
}

9、

#include <stdio.h>

#define SIZE 100

char *s_gets(char *st, int n);
void reverse(char *ar1);

int main(void)
{
    char st1[SIZE];
    
    printf("please input st1: "); s_gets(st1, SIZE);
    
    
    printf("origin  st1: %s
", st1);
    
    reverse(st1);
    
    printf("reverse st1: %s
", st1);
    
    return 0;
        
}

void reverse(char *ar1)
{
    int len = 0;
    
    while(*(ar1 + len))
    {
        len++;
    }
    
    int i;
    char temp;
    
    for(i = 0; i < len / 2; i++)
    {
        temp = ar1[i];
        ar1[i] = ar1[len - 1 - i];
        ar1[len - 1 - i] = temp;
    }
}

char *s_gets(char *st, int n)
{
    char *ret_val;
    int i = 0;
    
    ret_val = fgets(st, n, stdin);
    
    if(ret_val)
    {
        while(st[i] != '
' && st[i] != '')
            i++;
        
        if(st[i] == '
')
            st[i] = '';
        else
            while(getchar() != '
')
                continue;
    }
    return ret_val;
}

循环

#include <stdio.h>

#define SIZE 100

char *s_gets(char *st, int n);
void reverse(char *ar1);

int main(void)
{
    char st1[SIZE];
    
    while(1)
    {
        printf("please input st1(blank to quit): "); s_gets(st1, SIZE);
        if(st1[0] == '')
            break;
        printf("origin  st1: %s
", st1);
        reverse(st1);
        printf("reverse st1: %s
", st1);
    }
    return 0;    
}

void reverse(char *ar1)
{
    int len = 0;
    
    while(*(ar1 + len))
    {
        len++;
    }
    
    int i;
    char temp;
    
    for(i = 0; i < len / 2; i++)
    {
        temp = ar1[i];
        ar1[i] = ar1[len - 1 - i];
        ar1[len - 1 - i] = temp;
    }
}

char *s_gets(char *st, int n)
{
    char *ret_val;
    int i = 0;
    
    ret_val = fgets(st, n, stdin);
    
    if(ret_val)
    {
        while(st[i] != '
' && st[i] != '')
            i++;
        
        if(st[i] == '
')
            st[i] = '';
        else
            while(getchar() != '
')
                continue;
    }
    return ret_val;
}

#include <stdio.h>

#define SIZE 100

char *s_gets(char *st, int n);
void reverse(char *ar1);

int main(void)
{
    char st1[SIZE];
    
    while(*st1 != '
')
    {
        printf("please input st1(blank to quit): "); s_gets(st1, SIZE);
        if(st1[0] == '')
            break;
        printf("origin  st1: %s
", st1);
        reverse(st1);
        printf("reverse st1: %s
", st1);
    }
    return 0;    
}

void reverse(char *ar1)
{
    int len = 0;
    
    while(*(ar1 + len))
    {
        len++;
    }
    
    int i;
    char temp;
    
    for(i = 0; i < len / 2; i++)
    {
        temp = ar1[i];
        ar1[i] = ar1[len - 1 - i];
        ar1[len - 1 - i] = temp;
    }
}

char *s_gets(char *st, int n)
{
    char *ret_val;
    int i = 0;
    
    ret_val = fgets(st, n, stdin);
    
    if(ret_val)
    {
        while(st[i] != '
' && st[i] != '')
            i++;
        
        if(st[i] == '
')
            st[i] = '';
        else
            while(getchar() != '
')
                continue;
    }
    return ret_val;
}

#include <stdio.h>
#include <string.h>

#define SIZE 100

char * invert(char *ar);

int main(void)
{
    char st1[SIZE];
    printf("please input st1: "); fgets(st1, SIZE, stdin);
    
    while(*st1 != '
')
    {
        printf("origin st1: %s", st1);
        invert(st1);
        printf("invert st1: %s
", st1);

        printf("please input st1(blank to quit): ");
        fgets(st1, SIZE, stdin);
    }
    
    return 0;
}

char *invert(char *ar)
{
    int len = strlen(ar);
    
    char temp[len];
    
    int i;
    
    for(i = 0; i < len; i++)
    {
        *(temp + i) = *(ar + len - 1 - i);    
    }
    
    for(i = 0; i < len; i++)
    {
        *(ar + i) = *(temp + i);
    }
    
    return ar;
}

#include <stdio.h>
#include <string.h>

#define SIZE 100

char *invert(char *ar);
char *s_gets(char *st, int n);

int main(void)
{
    char st1[SIZE];
    printf("please input st1: "); s_gets(st1, SIZE);
    
    while(*st1 != '')
    {
        printf("origin st1: "); puts(st1);
        invert(st1);
        printf("invert st1: "); puts(st1);
        
        printf("please input st1(blank to quit): ");
        s_gets(st1, SIZE);
    }
    
    return 0;
}

char *invert(char *ar)
{
    int len = strlen(ar);
    
    char temp[len];
    int i;
    
    for(i = 0; i < len; i++)
    {
        *(temp + i) = *(ar + len - 1 - i);
    }
    for(i = 0; i < len; i++)
    {
        *(ar + i) = *(temp + i);
    }
        
    return ar;
}

char *s_gets(char *st, int n)
{
    char *ret_val;
    int i = 0;
    
    ret_val = fgets(st, n, stdin);
    
    if(ret_val)
    {
        while(st[i] != '
' && st[i] != '')
            i++;
        
        if(st[i] == '
')
            st[i] = '';
        else
            while(getchar() != '
')
                continue;
    }
    return ret_val;
}

10、

#include <stdio.h>

#define SIZE 100

char *s_gets(char *st, int n);
void del_space(char *ar);

int main(void)
{
    char st1[SIZE];
    
    printf("please input st1: "); s_gets(st1, SIZE);
    
    printf("origin st1: "); puts(st1);
    del_space(st1);
    printf("delete st1: "); puts(st1);
    
    return 0;
}

void del_space(char *ar)
{
    int i = 0;
    
    while(ar[i])
    {
        if(ar[i] == ' ')
        {
            int j = i;
            while(ar[i])
            {
                ar[i] = ar[i+1];
                i++; 
            }
            i = j;
        }
        else
        {
            i++;
        }
    }
}

char *s_gets(char *st, int n)
{
    char * ret_val;
    int i = 0;
    
    ret_val = fgets(st, n, stdin);
    
    if(ret_val)
    {
        while(st[i] != '
' && st[i] != '')
            i++;
        
        if(st[i] == '
')
            st[i] = '';
        else
            while(getchar() != '
')
                continue;
    }
    return ret_val;
}

#include <stdio.h>

#define SIZE 100

char *s_gets(char *st, int n);
void del_space(char *ar);

int main(void)
{
    char st1[SIZE];
    
    printf("please input st1: "); s_gets(st1, SIZE);
    
    while(*st1 != '')
    {
        printf("origin st1: "); puts(st1);
        del_space(st1);
        printf("delete st1: "); puts(st1);
        printf("please input st1(blank to quit): "); s_gets(st1, SIZE);
    }
    return 0;
}

void del_space(char *ar)
{
    int i = 0;
    
    while(ar[i])
    {
        if(ar[i] == ' ')
        {
            int j = i;
            while(ar[i])
            {
                ar[i] = ar[i+1];
                i++; 
            }
            i = j;
        }
        else
        {
            i++;
        }
    }
}

char *s_gets(char *st, int n)
{
    char * ret_val;
    int i = 0;
    
    ret_val = fgets(st, n, stdin);
    
    if(ret_val)
    {
        while(st[i] != '
' && st[i] != '')
            i++;
        
        if(st[i] == '
')
            st[i] = '';
        else
            while(getchar() != '
')
                continue;
    }
    return ret_val;
}

#include <stdio.h>

#define SIZE 100

char *s_gets(char *st, int n);
void del_space(char *ar);

int main(void)
{
    char st1[SIZE];
    
    printf("please input st1: "); s_gets(st1, SIZE);
    
    while(1)
    {
        printf("origin st1: "); puts(st1);
        del_space(st1);
        printf("delete st1: "); puts(st1);
        printf("please input st1(blank to quit): "); s_gets(st1, SIZE);
        if(st1[0] == '')
            break;
    }
    return 0;
}

void del_space(char *ar)
{
    int i = 0;
    
    while(ar[i])
    {
        if(ar[i] == ' ')
        {
            int j = i;
            while(ar[i])
            {
                ar[i] = ar[i+1];
                i++; 
            }
            i = j;
        }
        else
        {
            i++;
        }
    }
}

char *s_gets(char *st, int n)
{
    char * ret_val;
    int i = 0;
    
    ret_val = fgets(st, n, stdin);
    
    if(ret_val)
    {
        while(st[i] != '
' && st[i] != '')
            i++;
        
        if(st[i] == '
')
            st[i] = '';
        else
            while(getchar() != '
')
                continue;
    }
    return ret_val;
}

#include <stdio.h>

#define SIZE 100
void trim_space(char *ar);

int main(void)
{
    char st1[SIZE];
    
    printf("please input st1: "); fgets(st1, SIZE, stdin);
    
    while(*st1 != '
')
    {
        printf("origin st1: %s", st1);
        trim_space(st1);
        printf("trim_space st1: %s", st1);
        printf("please input st1(blank to quit): "); fgets(st1, SIZE, stdin);
    }
    
    return 0;
}

void trim_space(char *ar)
{
    char *temp;
    
    temp = ar;
    int count = 0;
    
    while(*ar)
    {
        if(*ar != ' ')
        {
            *temp++ = *ar++;
        }
        else
        {
            ar++;
            count++;
        }
    }
    while(count--)
        *temp++ = '';
}

#include <stdio.h>

#define SIZE 100
void trim_space(char *ar);

int main(void)
{
    char st1[SIZE];
    
    printf("please input st1: "); fgets(st1, SIZE, stdin);
    
    while(*st1 != '
')
    {
        printf("origin st1: %s", st1);
        trim_space(st1);
        printf("trim_space st1: %s", st1);
        printf("please input st1(blank to quit): "); fgets(st1, SIZE, stdin);
    }
    
    return 0;
}

void trim_space(char *ar)
{
    int i = 0;
    
    while(ar[i] != '')
    {
        if(ar[i] != ' ')
        {
            i++;
        }
        else
        {
            int j = i;
            while(ar[i] != '')
            {
                ar[i] = ar[i + 1];
                i++;
            }
            i = j;
        }
    }
}

#include <stdio.h>

#define SIZE 100
void trim_space(char *ar);

int main(void)
{
    char st1[SIZE];
    
    printf("please input st1: "); fgets(st1, SIZE, stdin);
    
    while(*st1 != '
')
    {
        printf("origin st1: %s", st1);
        trim_space(st1);
        printf("trim_space st1: %s", st1);
        printf("please input st1(blank to quit): "); fgets(st1, SIZE, stdin);
    }
    
    return 0;
}

void trim_space(char *ar)
{
    char *temp = ar;
    int count = 0;
    
    while(*ar != '')
    {
        if(*ar != ' ')
        {
            *temp++ = *ar++;
        }
        else
        {
            ar++;
            count++;
        }
    }
    while(count--)
        *temp++ = '';
}

11、

#include <stdio.h>
#include <string.h>
#include <stdbool.h>

#define SIZE 100
#define LIM 10

char *s_gets(char *st, int n);
char menu(void);
void print_origin(char ar[][100], int n);
void print_sort(char *ar[], int n);
void print_len(char *ar[], int n);
void print_first(char *ar[], int n);
int length(char *ar);

int main(void)
{
    char st1[LIM][SIZE];
    char *pt1[LIM];
    int ct = 0;
    printf("please input the strings, EOF to quit.
");
    while(ct < LIM && s_gets(st1[ct], SIZE) != NULL && st1[ct][0] != EOF)
    {
        pt1[ct] = st1[ct];
        ct++;
    }
    printf("please choose: 
");
    char ch = menu();
    while(ch != 'q')
    {   
        switch (ch)
        {
            case 'a': print_origin(st1, ct); break;
            case 'b': print_sort(pt1, ct); break;
            case 'c': print_len(pt1, ct); break;
            case 'd': print_first(pt1, ct); break;
            case 'q': break;
            default: printf("a-d or q pleawe");
        }
        ch = menu();
    }
    return 0;
}

char menu(void)
{
    printf("please input your choice!
");
    printf("a) print origin         b) print sort by ASCII
");
    printf("c) print by length      d) print by first word length
");
    printf("q) quit
");
    
    char ch = getchar();
    
    while(getchar() != '
')
        continue;
        
    return ch;
}

char *s_gets(char *st, int n)
{
    char * ret_val;
    int i = 0;
    
    ret_val = fgets(st, n, stdin);
    
    if(ret_val)
    {
        while(st[i] != '
' && st[i] != '')
            i++;
        
        if(st[i] == '
')
            st[i] = '';
        else
            while(getchar() != '
')
                continue;   
    } 
    return ret_val;
}

void print_origin(char ar[][100], int n)
{
    int i;
    puts("show the origin: ");
    for(i = 0; i < n; i++)
    {
        puts(ar[i]);
    }
    putchar('
');
}

void print_sort(char *ar[], int n)
{
    char *temp;
    int i, j;
    
    for(i = 0; i < n - 1; i++)
    {
        for(j = i + 1; j < n; j++)
        {
            if(strcmp(ar[i], ar[j]) > 0)
            {
                temp = ar[i];
                ar[i] = ar[j];
                ar[j] = temp; 
            }
        }
    }
    puts("
Here is the sorted by ASCII:");
    for(i = 0; i < n; i++)
    {
        puts(ar[i]);
    }
    putchar('
');
}

void print_len(char *ar[], int n)
{
    char *temp;
    int i, j;
    
    for(i = 0; i < n - 1; i++)
    {
        for(j = i + 1; j < n; j++)
        {
            if(strlen(ar[i]) > strlen(ar[j]))
            {
                temp = ar[i];
                ar[i] = ar[j];
                ar[j] = temp;
            }
        }
    }
    puts("
Here is show by length: ");
    for(i = 0; i < n; i++)
    {
        puts(ar[i]);
    }
    putchar('
');
}

void print_first(char *ar[], int n)
{
    char *temp;
    int i, j;
    
    for(i = 0; i < n - 1; i++)
    {
        for(j = i + 1; j < n; j++)
        {
            if(length(ar[i]) > length(ar[j]))
            {
                temp = ar[i];
                ar[i] = ar[j];
                ar[j] = temp;
            }
        }
    }
    puts("show the result sort by first word.");
    for(i = 0; i < n; i++)
    {
        puts(ar[i]);
    }
    putchar('
');
}

int length(char *ar)
{
    int i = 0;
    int j = 0;
    bool inword = false;
    
    while(ar[i] != '')
    {
        if(inword == false && ar[i] != ' ')
            inword = true;
        if(inword == true && ar[i] != ' ')
            j++;
        if(inword == true && ar[i] == ' ')
            break;
        i++;
    }
    
    if(j != 0)
        return j;
    else
        return i;
}

12、

#include <stdio.h>
#include <ctype.h>
#include <stdbool.h>

void basic(void);

int main(void)
{
    printf("please input strings(EOF to quit): 
");
    basic();
    
    return 0;
}

void basic(void)
{
    char ch;
    int words = 0;
    int upper = 0;
    int lower = 0;
    int punct = 0;
    int digit = 0;
    bool inword = false;
    
    while((ch = getchar()) != EOF)
    {
        if(!isspace(ch) && inword == false)
        {
            words++;
            inword = true;
        }
        
        if(isspace(ch) && inword == true)
        {
            inword = false;
        }
        
        if(isupper(ch))
        {
            upper++;
        }
        
        if(islower(ch))
        {
            lower++;    
        } 
        
        if(ispunct(ch))
        {
            punct++;
        }
        
        if(isdigit(ch))
        {
            digit++;
        }
    }
    printf("words: %d
", words);
    printf("upper: %d
", upper);
    printf("lower: %d
", lower);
    printf("punct: %d
", punct);
    printf("digit: %d
", digit);
}

循环

#include <stdio.h>
#include <ctype.h>
#include <stdbool.h>

void basic(void);

int main(void)
{
    char ch;
    while(1)
    {
        printf("please input strings(EOF to quit): 
");
        basic();
        
        printf("blank to quit, other to contine: ");
        ch = getchar();
        
        if(ch == '
')
            break;
            
        while(getchar() != '
')
            continue; 
        
    }
    return 0;
}

void basic(void)
{
    char ch;
    int words = 0;
    int upper = 0;
    int lower = 0;
    int punct = 0;
    int digit = 0;
    bool inword = false;
    
    while((ch = getchar()) != EOF)
    {
        if(!isspace(ch) && inword == false)
        {
            words++;
            inword = true;
        }
        
        if(isspace(ch) && inword == true)
        {
            inword = false;
        }
        
        if(isupper(ch))
        {
            upper++;
        }
        
        if(islower(ch))
        {
            lower++;    
        } 
        
        if(ispunct(ch))
        {
            punct++;
        }
        
        if(isdigit(ch))
        {
            digit++;
        }
    }
    printf("words: %d
", words);
    printf("upper: %d
", upper);
    printf("lower: %d
", lower);
    printf("punct: %d
", punct);
    printf("digit: %d
", digit);
}

#include <stdio.h>
#include <ctype.h>

#define SIZE 256

int check_words(char *input);
int check_upper(char *input);
int check_lower(char *input);
int check_punct(char *input);
int check_digit(char *input);

int main(void)
{
    char input[SIZE];
    int i = 0;
    
    while((input[i++] = getchar()) != EOF)
    {
        if(i > SIZE)
        {
            printf("over flowed
");
            break;    
        }    
    }    
    
    printf("basic static is below: 
");
    printf("input words: %d
", check_words(input));
    printf("upper   num: %d
", check_upper(input));
    printf("lower   num: %d
", check_lower(input));
    printf("punct   num: %d
", check_punct(input));
    printf("digit   num: %d
", check_digit(input));
    
    return 0;
} 

int check_words(char *input)
{
    int count = 0;
    int start = 0;
    
    while(*input != EOF)
    {
        if(isalpha(*input) == 0 && start == 0)
        {
            input++;
        }
        else if(isalpha(*input) == 0 && start == 1)
        {
            count++;
            input++;
            start = 0;
        }
        else if(isalpha(*input) != 0)
        {
            start = 1;
            input++; 
        }
    }
    if(start == 1)
        count++;
    return count;
}

int check_upper(char *input)
{
    int count = 0;
    
    while(*input != EOF)
    {
        if(isupper(*input++) != 0)
        {
            count++;
        }
        
    }
    return count;
}

int check_lower(char *input)
{
    int count = 0;
    
    while(*input != EOF)
    {
        if(islower(*input++) != 0)
        {
            count++;
        }
    }
    return count;
}

int check_punct(char *input)
{
    int count = 0;
    
    while(*input != EOF)
    {
        if(ispunct(*input++) != 0)
            count++;
    }
    return count;
}

int check_digit(char *input)
{
    int count = 0;
    
    while(*input != EOF)
    {
        if(isdigit(*input++) != 0)
            count++;
    }
    
    return count;
}

#include <stdio.h>
#include <ctype.h>

#define SIZE 500

int words_check(char *ar);
int upper_check(char *ar);
int lower_check(char *ar);
int punct_check(char *ar);
int digit_check(char *ar);

int main(void)
{
    char input[SIZE];
    int i = 0;
    
    puts("please input the strings.");
    while((input[i++] = getchar()) != EOF)
    {
        if(i > SIZE)
        {
            puts("number overflow!");
            break;
        }
    }
    
    puts("basic statics is below: ");
    printf("words num: %d
", words_check(input));
    printf("upper num: %d
", upper_check(input));
    printf("lower num: %d
", lower_check(input));
    printf("punct num: %d
", punct_check(input));
    printf("digit num: %d
", digit_check(input));
    
    return 0;
}

int words_check(char *ar)
{
    int count = 0;
    int start = 0;
    
    while(*ar != EOF)
    {
        if(isalpha(*ar) == 0 && start == 0)
        {
            ar++;
        }
        if(isalpha(*ar) == 0 && start == 1)
        {
            count++;
            ar++;
            start = 0;
        }
        if(isalpha(*ar) != 0)
        {
            ar++;
            start = 1;
        }
    }
    if(start == 1)
        count++;
    return count;
}

int upper_check(char *ar)
{
    int count = 0;
    
    while(*ar != EOF)
    {
        if(isupper(*ar++) != 0)
            count++;
    }
    return count;
}

int lower_check(char *ar)
{
    int count = 0;
    
    while(*ar != EOF)
    {
        if(islower(*ar++) != 0)
        {
            count++;
        }
    }
    return count;
}

int punct_check(char *ar)
{
    int count = 0;
    
    while(*ar != EOF)
    {
        if(ispunct(*ar++) != 0)
        {
            count++;
        }
    }
    return count;
}

int digit_check(char *ar)
{
    int count = 0;
    
    while(*ar != EOF)
    {
        if(isdigit(*ar++) != 0)
        {
            count++;
        }
    }
    return count;
}

13、

#include <stdio.h>

void revert(char *ar);

int main(int argc, char *argv[])
{
    int i = 0;
    
    for(i = 1; i < argc; i++)
    {
        printf("%s ", argv[argc - i]);
    }
    putchar('
');
    
    return 0;
}

#include <stdio.h>

void revert(char *ar);

int main(int argc, char *argv[])
{
    int i = 0;
    if(argc < 2)
    {
        puts("two few arguments");
    }
    else
    {
        for(i = 1; i < argc; i++)
        {
            printf("%s ", argv[argc - i]);
        }
        putchar('
');
    }
        
    return 0;
}

#include <stdio.h>

void revert(char *ar);

int main(int argc, char *argv[])
{
    int i = 0;
    if(argc < 2)
    {
        puts("two few arguments");
    }
    else
    {
        for(i = argc; i > 1; i--)
        {
            printf("%s ", argv[i - 1]);
        }
        putchar('
');
    }
        
    return 0;
}

14、

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char * argv[])
{
    int i;
    double power = 1.0;
    
    double argv_1 = atof(argv[1]);
    int argv_2 = atoi(argv[2]);
    
    if(argc != 3)
    {
        printf("argument error!");    
    } 
    else
    {
        for(i = 0; i < argv_2; i++ )
            power *= argv_1;
    }
    
    printf("power: %.2f
", power);
    
    return 0;
}

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char * argv[])
{
    int i;
    double power = 1.0;
    
    double argv_1 = atof(argv[1]);
    int argv_2 = atoi(argv[2]);
    
    if(argc != 3)
    {
        printf("argument error! only %d argument!
", argc);
        return 0;
    } 
    else
    {
        for(i = 0; i < argv_2; i++ )
            power *= argv_1;
    }
    
    printf("power: %.2f
", power);
    
    return 0;
}

15、

#include <stdio.h>
#include <ctype.h>

#define SIZE 100

int convert_int(char *ar);
char *s_gets(char *st, int n);

int main(void)
{
    int result;
    char st1[SIZE];
    
    printf("st1: "); s_gets(st1, SIZE);
    
    printf("result: %d
",convert_int(st1));
    
    return 0;
}

int convert_int(char *ar)
{
    int i = 0;
    
    while(ar[i] != '' && isdigit(ar[i]))
        i++;
    
    if(ar[i] != '')
    {
        puts("not all digits!");
        return 0;
    }
    else
    {
        int len = 0;
        while(ar[len] != '')
            len++;
        
        i = 0;
        int j;
        int temp; 
        int result = 0;
        
        while(ar[i] != '')
        {
            temp = 1;
            int num = ar[i] - '0';
            for(j = 0; j < len - 1 - i; j++)
            {
                temp *= 10;
            }
            result = result + num * temp;
            i++;
        }
        return result;
    }
}

char *s_gets(char *st, int n)
{
    char *ret_val;
    int i = 0;
    
    ret_val = fgets(st, n, stdin);
    
    if(ret_val)
    {
        while(st[i] != '
' && st[i] != '')
            i++;
        
        if(st[i] == '
')
            st[i] = '';
        else
            while(getchar() != '
')
                continue;
    }
    return ret_val;
}

 

#include <stdio.h>
#include <ctype.h>

#define SIZE 100

int convert_int(char *ar);
char *s_gets(char *st, int n);

int main(void)
{
    int result;
    char st1[SIZE];
    
    printf("st1: "); s_gets(st1, SIZE);
    
    while(st1[0] != '')
    {
        printf("result: %d
",convert_int(st1));
        printf("st1(blank to quit): "); s_gets(st1, SIZE);
    }
    
    return 0;
}

int convert_int(char *ar)
{
    int i = 0;
    
    while(ar[i] != '' && isdigit(ar[i]))
        i++;
    
    if(ar[i] != '')
    {
        puts("not all digits!");
        return 0;
    }
    else
    {
        int len = 0;
        while(ar[len] != '')
            len++;
        
        i = 0;
        int j;
        int temp; 
        int result = 0;
        
        while(ar[i] != '')
        {
            temp = 1;
            int num = ar[i] - '0';
            for(j = 0; j < len - 1 - i; j++)
            {
                temp *= 10;
            }
            result = result + num * temp;
            i++;
        }
        return result;
    }
}

char *s_gets(char *st, int n)
{
    char *ret_val;
    int i = 0;
    
    ret_val = fgets(st, n, stdin);
    
    if(ret_val)
    {
        while(st[i] != '
' && st[i] != '')
            i++;
        
        if(st[i] == '
')
            st[i] = '';
        else
            while(getchar() != '
')
                continue;
    }
    return ret_val;
}

#include <stdio.h>
#include <ctype.h>
#include <string.h>

#define SIZE 100

int str_int(char *ar);

int main(void)
{
    char st1[SIZE];
    printf("please input st1: "); scanf("%s", st1);
    
    printf("convert result: %d
", str_int(st1));
    
    return 0;
}

int str_int(char *ar)
{
    int len = 0;
    len = strlen(ar);
    int result = 0;
    int i;
    int temp = 1;
    
    
    for(i = len - 1; i >= 0; i--)
    {
        if(isdigit(ar[i]) == 0)
        {
            puts("not all digit!");
            return 0;    
        } 
        result =  result + (ar[i] - '0') * temp;
        temp *= 10;
    }
    
    return result;
}

 

循环：

#include <stdio.h>
#include <ctype.h>
#include <string.h>

#define SIZE 100

int str_int(char *ar);

int main(void)
{
    char st1[SIZE];
    
    printf("please input st1: "); scanf("%s", st1);
    while(1)
    {
        printf("convert result: %d
", str_int(st1));
        printf("please input st1(q to quit): "); scanf("%s", st1);
        if(st1[0] == 'q')
            break;
    }
    return 0;
}

int str_int(char *ar)
{
    int len = 0;
    len = strlen(ar);
    int result = 0;
    int i;
    int temp = 1;
    
    
    for(i = len - 1; i >= 0; i--)
    {
        if(isdigit(ar[i]) == 0)
        {
            puts("not all digit!");
            return 0;    
        } 
        result =  result + (ar[i] - '0') * temp;
        temp *= 10;
    }
    
    return result;
}

#include <stdio.h>
#include <ctype.h>
#include <string.h>

#define SIZE 100

int convert(char *ar);

int main(void)
{
    char st1[SIZE];
    printf("please input st1: "); scanf("%s", st1);
    
    printf("convert result: %d
", convert(st1));
    
    return 0;
}

int convert(char *ar)
{
    int len = strlen(ar);
    
    int i;
    int temp = 1;
    int result = 0;
    
    for(i = len; i > 0; i--)
    {
        if(isdigit(*(ar + i - 1)) == 0)
        {
            puts("not all digit!");
            return 0;
        }
        result = result + (*(ar + i - 1) - '0') * temp;
        temp *= 10;
    }
    return result;
}

 

循环：

#include <stdio.h>
#include <ctype.h>
#include <string.h>

#define SIZE 100

int convert(char *ar);

int main(void)
{
    char st1[SIZE];
    
    printf("please input st1: "); scanf("%s", st1);
    while(1)
    {
        printf("convert result: %d
", convert(st1));
        printf("please input st1(q to break): "); scanf("%s", st1);
        if(st1[0] == 'q')
            break;
    }
    return 0;
}

int convert(char *ar)
{
    int len = strlen(ar);
    
    int i;
    int temp = 1;
    int result = 0;
    
    for(i = len; i > 0; i--)
    {
        if(isdigit(*(ar + i - 1)) == 0)
        {
            puts("not all digit!");
            return 0;
        }
        result = result + (*(ar + i - 1) - '0') * temp;
        temp *= 10;
    }
    return result;
}

16、

#include <stdio.h>
#include <string.h>


void to_upper(char *ar);
void to_lower(char *ar);

int main(void)
{
    char st1[100] = "abCDEF";
    
    puts("upper: ");
    to_upper(st1);
    
    puts("
lower: ");
    to_lower(st1);
    
    return 0; 
}

void to_upper(char *ar)
{
    int i;
    
    while(*(ar + i))
    {
        *(ar + i) = toupper(*(ar + i));
        i++;
    }
    puts(ar);
}

void to_lower(char *ar)
{
    int i;
    
    while(*(ar + i))
    {
        *(ar + i) = tolower(*(ar + i));
        i++;
    }
    
    puts(ar);
}

16、

#include <stdio.h>
#include <ctype.h>
#include <string.h>

#define SIZE 256

void printf_orig(char *st);
void printf_upper(char *st);
void printf_lower(char *st);

int main(int argc, char *argv[])
{
    char c;
    if(argc < 2)
    {
        c = 'p';
    }
    else
        c = argv[1][1];
    
    char test[SIZE];
    
    printf("please input the string: ");
    fgets(test, SIZE, stdin);
    
    switch(c)
    {
        case 'p':
        case 'P': printf_orig(test); break;
        
        case 'u': 
        case 'U': printf_upper(test); break;
        
        case 'l':
        case 'L': printf_lower(test); break;
    }
    
    return 0;
}

void printf_orig(char *st)
{
    puts("result: ");
    puts(st);
}

void printf_upper(char *st)
{
    int i = 0;
    
    while(*(st + i))
    {
        *(st + i) = toupper(*(st + i));
        i++;
    }
    puts("result: ");
    puts(st);
}

void printf_lower(char *st)
{
    int i = 0;
    
    while(*(st + i))
    {
        *(st + i) = tolower(*(st + i));
        i++;
    }
    puts("result: ");
    puts(st);
}

#include <stdio.h>
#include <ctype.h>
#include <string.h>

#define SIZE 256

void printf_orig(char *st);
void printf_upper(char *st);
void printf_lower(char *st);

int main(char argc, char *argv[])
{
    char c;
    if(argc < 2)
    {
        c = 'p';
    }
    else
    {
        c = argv[1][1];
    }
    
    char test[SIZE];
    printf("please input the string: "); fgets(test, SIZE, stdin);
    
    switch(c)
    {
        case 'p':
        case 'P': printf_orig(test); break;
        
        case 'u':
        case 'U': printf_upper(test); break;
        
        case 'l':
        case 'L': printf_lower(test); break; 
    }
    return 0;
}

void printf_orig(char *st)
{
    printf("origin: %s
", st);
}

void printf_upper(char *st)
{
    printf("upper: ");
    while(*st != EOF && *st != '')
    {
        putchar(toupper(*st++));
    }
    putchar('
');
}

void printf_lower(char *st)
{
    printf("lower: ");
    
    while(*st != EOF && *st != '')
    {
        putchar(tolower(*st++));
    }
    putchar('
');
}

#include <stdio.h>
#include <ctype.h>

#define SIZE 100

void print_orig(char *ar);
void print_upper(char *ar);
void print_lower(char *ar);

int main(int argc, char *argv[])
{
    char ch;
    
    
    if(argc < 2)
    {
        ch = 'p';
    }
    else
    {
        ch = argv[1][1];
    }
    
    char st1[SIZE];
    printf("please input the string: "); fgets(st1, SIZE, stdin);
    
    switch(ch)
    {
        case 'p':
        case 'P': print_orig(st1); break;
        
        case 'u':
        case 'U': print_upper(st1); break;
        
        case 'l':
        case 'L': print_lower(st1); break;
    }
    return 0;    
} 

void print_orig(char *st)
{
    printf("origin: %s
", st);
}

void print_upper(char *st)
{
    printf("upper: ");
    
    while(*st != '')
    {
        putchar(toupper(*st++));
    }
}

void print_lower(char *st)
{
    printf("lower: ");
    
    while(*st != '')
    {
        putchar(tolower(*st++));
    }
}

#include <stdio.h>
#include <string.h>
#include <ctype.h>

#define SIZE 80
#define NUMBER 5

void show_menu(void);
void input_string(int number, char st[][SIZE]);
void print_original(int number, char st[][SIZE]);
void print_ascii(int number, char st[][SIZE]);
void print_length(int number, char st[][SIZE]);
void print_words(int number, char st[][SIZE]);
void sort_order(int number, int order[][2]);
int get_word_length(char *input);

int main(void)
{
    char test[NUMBER][SIZE];
    int selected;
    input_string(NUMBER, test);
    show_menu();
    
    while(scanf("%d", &selected) != 1)
    {
        printf("please input intiger.
");
        while(getchar() != '
')
            continue;
    }
    
    while(selected != 5)
    {
        switch(selected)
        {
            case 1: print_original(NUMBER, test); break;
            case 2: print_ascii(NUMBER, test); break;
            case 3: print_length(NUMBER, test); break;
            case 4: print_words(NUMBER, test); break;
            case 5: break;
            default: printf("Error select, retry!
");
        }
        show_menu();
        while(scanf("%d", &selected) != 1)
        {
            printf("please input intiger.
");
            while(getchar() != '
')
                continue;
        }
    }
    printf("All done, bye.");
}

void show_menu()
{
    puts("================================================================
");
    printf("1) print original strings            2) print string by ascii order
");
    printf("3) print string by length            4) print string by word length
");
    printf("5) quit
");
    puts("
==============================================================
");
}

void input_string(int number, char st[][SIZE])
{
    printf("please intput 5 strings seperate by enter.
");
    int i;
    for(i = 0; i < number; i++)
    {
        fgets(st[i], SIZE, stdin);
    }
}

void print_original(int number, char st[][SIZE])
{
    printf("print 5 strings in original mode.
");
    int i;
    for(i = 0; i < number; i++)
    {
        printf("%d  %s", i, st[i]);
    }
}

void print_ascii(int number, char st[][SIZE])
{
    printf("print 5 strings in ascii order.
");
    int order[number][2];
    int i;
    
    for(i = 0; i < number; i++)
    {
        order[i][0] = i;
        order[i][1] = st[i][0];
    }
    
    sort_order(number, order);
    
    for(i = 0; i <number; i++)
    {
        printf("ASCII  NO. %d. %s", i, st[order[i][0]]);
    }
    
}

void print_length(int number, char st[][SIZE])
{
    printf("print 5 strings in length mode.
");
    int order[number][2];
    int i;
    
    for(i = 0; i < number; i++)
    {
        order[i][0] = i;
        order[i][1] = strlen(st[i]);
    }
    
    sort_order(number, order);
    
    for(i = 0; i < number; i++)
    {
        printf("length NO. %d. %s", i, st[order[i][0]]);
    }
}

void print_words(int number, char st[][SIZE])
{
    printf("print 5 strings in words mode
");
    int order[number][2];
    int i;
    
    for(i = 0; i < number; i++)
    {
        order[i][0] = i;
        order[i][1] = get_word_length(st[i]);
    }
    
    sort_order(number, order);
    
    for(i = 0; i < number; i++)
    {
        printf("words NO. %d. %s", i, st[order[i][0]]);
    }
}

void sort_order(int number, int order[][2])
{
    int temp[2];
    int i, j;
    
    for(i = 0; i < number - 1; i++)
    {
        for(j = 0; j < number - 1 - i; j++)
        {
            if(order[j][1] > order[j + 1][1])
            {
                temp[0] = order[j][0];
                temp[1] = order[j][1];
                order[j][0] = order[j + 1][0];
                order[j][1] = order[j + 1][1];
                order[j + 1][0] = temp[0];
                order[j + 1][1] = temp[1];
            }
        }
    }
}

int  get_word_length(char *input)
{
    char *in = input;
    int length = 0;
    
    while(isalpha(*in) == 0)
    {
        in++;
    }
    
    while(isalpha(*in) != 0)
    {
        in++;
        length++;    
    }
    
    return length;
}