c語言：判斷一個字符串中是否含有字符C

#include <stdio.h>
int is_in(char *s, char c)
{
while (*s != '\0')
{
if (*s == c)
{
return 1;
}
else
{
s++;
}
}
return 0;
}

int main()
{
char *p = "abcdefgh";
char c = 'd';
int ret = is_in(p,c);
if (ret == 1)
{
printf("存在\n");
}
else
{
printf("不存在\n");
}
return 0;
}