关于字符串的一些算法

// programmer_string_test.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include "stdio.h"
#include <iostream>
#include "assert.h"
#include <string>
using namespace std;
#define MAX 50

/*不用itoa函数，将整数转化成字符串数*/
void itoa_test()
{
    int num,i,j=0;
    char a[MAX],b[MAX];
    cout << "please input a interger:" << endl;
    cin >> num;
    while(num)
    {
        i=num%10;
        a[j]=i+'0';
        j++;
        num/=10;
    };
    a[j]='\0';
    cout << "the inverted string is : " << a << endl;
    
    //求出来的a是倒转的，现将其再转回去
    for(j=0;j<strlen(a);j++)
    {
        b[j]=a[strlen(a)-j-1];
    }
    b[j]='\0';

    cout << " the converted string is :" << endl
        << b << endl;
}

/* 不用atoi函数，将字符串转换成整数*/
void atoi_test()
{
    cout << " atoi_test: " << endl;
    char a[MAX];
    int i,num=0,len;
    cout << "please input a num string: " << endl;
    cin.getline(a,MAX);
    len=strlen(a);
    for(i=0;i<len;i++)
    {
        num=num*10+a[i]-'0';
    }

    cout << " the convered number is " << num << endl;
}

/* strcpy test */
char * strcpy_fun(char *dest, char *src)
{
    int i,len;
    len=strlen(src);
    cout <<" the len of src is " << len << endl;
    for(i=0;i<len;i++)
        *dest++=*src++;
    cout << " i is " << i <<endl;
    dest[i]='\0';
    char c;
    for(i=0;i<5;i++)
    {
        c=dest[i];
        cout << c << endl;
    }
    return dest;
}

char *strcpy_answer(char *dest, const char *src)
{
    assert((dest!=NULL) && (src !=NULL));
    char *address=dest;
    while((*dest++=*src++)!='\0');
    return address;
}

void strcpy_test()
{
    cout << "strcpy_test: " << endl;
    char dest[5],dest1[5],src[5]="hi";
    strcpy_fun(dest,src);
    strcpy_answer(dest1,src);
    
    cout <<" the dest string is " << dest << endl;
    cout <<" the programmer answer is : "<< dest1 <<endl;
}


char *string_shift_fun(char *str, int steps)
{
    char tmp[MAX];
    int len,i;
    len=strlen(str);
    for(i=0;i<steps;i++)
        tmp[i]=str[len-steps+i];
    for(i=0;i<(len-steps);i++)
        tmp[steps+i]=str[i];
    tmp[len]='\0';
    strcpy(str,tmp);
    cout << "the tmp is :" <<tmp << endl;
    return str;
}

void string_shift_answer(char *pStr,int steps)
{
    int n=strlen(pStr)-steps;
    char tmp[MAX];
    memcpy(tmp,pStr+n,steps);
    memcpy(tmp+steps,pStr,n);
    memcpy(pStr,tmp,strlen(pStr));
}

void string_shift_test()
{
    /*
    cout << "string_shift_test:" << endl;
    char str[MAX],*str1;
    cin.getline(str,10);
    */
    char str[]="hello",*str1;
    str1=string_shift_fun(str,2);
    
    cout << "the shifted string is:"<< str1 << endl;

    string_shift_answer(str,2);
    cout << "shifted angain:the shifted string of programer answer is :" << str << endl;
}


//找出字符串中出现的相同且长度最长的字符串，输出它的及其首字符的位置
int longest_same_string_answer()
{
    string str,tep;
    cout << "please input string :" << endl;
    cin >> str;

    for(int i=str.length()-1;i>1;i--)
        for(int j=0;j<str.length();j++)
            if(j+i<=str.length())
            {
                size_t t=0;
                size_t num=0;
                tep=str.substr(j,i);
                t=str.find(tep);
                num=str.rfind(tep);
                if(t!=num)
                {
                    cout << tep << " " << t+1 <<endl;
                    return 0;
                }
            }
    return 0;
}

//返回主串中字符字串以后的所有字符
int substr_afterstr_fun(char *str,char *substr)
{
    int len,sublen,i=0,j=0;
    len=strlen(str);
    sublen=strlen(substr);

    while(i<len&&j<sublen)
    {
            if(str[i]==substr[j])
            {
                i++;
                j++;
            }
            else
            {
                i=i-j+1;
                j=0;
            }
    }
    if(j>=sublen)
        return (i-sublen);
}
    
void substr_afterstr()
{
    char str[]="hellostrhaha",substr[]="str";
    int pos;
    pos=substr_afterstr_fun(str,substr);
    cout << "the string begin with the sub string is :" << str+pos << endl;

}


//将一句话里的单词倒转，标点符号不倒转
void invert_fun(char *str)
{
    int len ,i;
    char tmp[MAX];
    len=strlen(str);
    for(i=0;i<len;i++)
        tmp[i]=str[len-1-i];
    tmp[len]='\0';
    strcpy(str,tmp);
}

void invert_word()
{
    char str[]="I come from tianjin.",tmp[MAX],word[MAX];
    int len,i=0,j=0,k,m;
    len=strlen(str);
    invert_fun(str);

    cout << "the totally invert string is:"<< str << endl;


    while(i<len)
    {
        word[j++]=str[i++];
        if(str[i]==' ')
        {
            word[j]='\0';
            invert_fun(word);
            for(k=0;k<strlen(word);k++)
                str[i-j+k]=word[k];
            j=0;
            i++;
        }
    }

    cout << "the invert string is :" << str << endl;
}


int _tmain(int argc, _TCHAR* argv[])
{
    //write a user defined function about itoa
    //itoa_test();
    
    //
    //atoi_test();

    //
    //strcpy_test();
    
    //
    //string_shift_test();

    //
    //longest_same_string_answer();
    
    //
    //substr_afterstr();

    //
    invert_word();
    while(1);
    return 0;
}