C Primer Plus（第六版）11.13 编程练习 第6题

#include<stdio.h>

#define SIZE 40

int is_within(char ch,char str[]);

int main(void)

{

int i = 0;

char *p;

char ch;

char store[SIZE] = "abcd";

while(ch!='q')

{

printf("q to quit\n");

scanf("%c",&ch);

while (getchar() != '\n')

continue;

i = is_within(ch,store);

if(i!=0)

printf("%c在%s第%d位\n",ch,store,i);

else printf("没找到%c\n",ch);

}

return 0;

}

int is_within(char ch,char str[])

{

char *p=NULL;

int i=0;

while(i<sizeof(str))

{

if(str[i] == ch)

{

p=&str[i];

}

i++;

}

if(p==NULL)

return 0;

else

return (p-str+1);

}