#include <stdio.h>

int main()
{
   char str[1000], ch;
   int i, frequency = 0;

   printf("输入字符串: ");
   fgets(str, (sizeof str / sizeof str[0]), stdin);

   printf("输入要查找的字符: ");
   scanf("%c",&ch);

   for(i = 0; str[i] != '\0'; ++i)
   {
       if(ch == str[i])
           ++frequency;
   }

   printf("字符 %c 在字符串中出现的次数为 %d", ch, frequency);

   return 0;
}

输入字符串: nowcoder
输入要查找的字符: o
字符 o 在字符串中出现的次数为 2