p319.3
1 #include<stdio.h> 2 #include<stdlib.h> 3 #include<ctype.h> 4 #include<string.h> 5 void deliver(char *a1, char *a2, int n); 6 7 int main(void) 8 { 9 int n; 10 char str1[81], *ptr, ar[81]; 11 ptr=gets(str1); 12 n=strlen(ptr); 13 deliver(ar, ptr, n); 14 puts(ar); 15 16 system("pause"); 17 return 0; 18 } 19 20 void deliver(char *a1, char *a2, int n) 21 { 22 int i; 23 for(i=0; i<n; i++){ 24 *(a1+i)=*(a2+i); 25 if(isspace(*(a1+i))) 26 break; 27 } 28 if(i==n) 29 *(a1+i)=' '; 30 else 31 *(a1+i+1)=' '; 32 }
p320.5
1 #include<stdio.h> 2 #include<stdlib.h> 3 int is_within(char *ar, char ch); 4 5 int main(void) 6 { 7 char ar[81], ch; 8 do 9 { 10 puts("input a range string:"); 11 gets(ar); 12 puts("input match char(enter q to quit):"); 13 ch=getchar(); 14 getchar(); 15 if(is_within(ar, ch)) puts("match"); 16 else puts("can't find"); 17 18 }while(ch!='q'); 19 20 system("pause"); 21 return 0; 22 } 23 24 int is_within(char *ar, char ch) 25 { 26 while(*ar!=' ') 27 if(*ar==ch) 28 return 1; 29 else 30 ar++; 31 return 0; 32 }
p320.6
1 #include<stdio.h> 2 #include<stdlib.h> 3 #include<string.h> 4 char *strncpy(char *s1, char *s2, int n); 5 6 int main(void) 7 { 8 char s1[81], s2[81]; 9 int n; 10 puts("please input a range string for s2:"); 11 gets(s2); 12 puts("please input a range string for s1:"); 13 gets(s1); 14 puts("please input a number of copies:"); 15 scanf("%d", &n); 16 getchar(); 17 18 strncpy(s1, s2, n); 19 puts(s1); 20 21 system("pause"); 22 return 0; 23 } 24 25 char *strncpy(char *s1, char *s2, int n) 26 { 27 int i; 28 29 if(n<=strlen(s2)){ 30 for(i=0; i<n; i++) 31 *(s1+i)=*(s2+i); 32 *(s1+i)=' '; 33 } 34 35 else if(n>strlen(s2)){ 36 for(i=0; i<strlen(s2); i++) 37 *(s1+i)=*(s2+i); 38 while(i<n){ 39 *(s1+i)=' '; 40 i++; 41 } 42 } 43 return s1; 44 }
参考答案给的strncpy()定义如下：
1 char *mystrncpy(char *p1, char *p2, int n) 2 { 3 char *p=p1; 4 while(*p1++ != ' ') continue; 5 *--p1 = *p2; 6 n--; 7 while(n>0 && *p2 != ' ') { 8 *++p1 = *++p2; 9 n--; 10 } 11 return p; 12 ｝