用C语言编写函数 统计子串sub在母串中的出现次数

以下是用C语言编写函数统计子串在母串中出现次数的示例代码：

#include <stdio.h>
#include <string.h>

int countSubstring(char *str, char *sub) {
    int count = 0;
    int len1 = strlen(str);
    int len2 = strlen(sub);
    for (int i = 0; i <= len1 - len2; i++) {
        int j;
        for (j = 0; j < len2; j++) {
            if (str[i + j] != sub[j]) {
                break;
            }
        }
        if (j == len2) {
            count++;
        }
    }
    return count;
}

int main() {
    char str[] = "hello world, world is beautiful";
    char sub[] = "world";
    int count = countSubstring(str, sub);
    printf("'%s' appears %d times in '%s'\n", sub, count, str);
    return 0;
}

输出结果为：

'world' appears 2 times in 'hello world, world is beautiful'