输入一个字符串,计算字符串中子串出现的次数

#include <stdio.h>

int mystrlen(const char *str)

{

int length = 0;

while (*str++)

{

length++;

}

return length;

}

char* mystrstr(const char *str, const char *sub)   //寻找字串，找到则返回该地址

{

int n = 0;

if (sub != NULL)

{

while (*str)

{

for (n = 0; (*(str + n) == *(sub + n)); n++)

{

if (*(sub + n + 1) == '\0')

{

return (char *)str;

}

}

str++;

}

return NULL;

}

else

{

return (char *)str;

}

}

int Substring(char *str, const char *sub)

{

char *p = str;

int count = 0;

int sublen = mystrlen(sub);

p = mystrstr(p, sub); //在主串中寻找字串

while (p != NULL)

{

count++;   //找到就计数器加1，让主串指针指向该字串之后一位继续寻找

p += sublen;

p = mystrstr(p, sub);

}

return count;

}

int main()

{

char str[100] = {0};

char sub[100] = {0};

int count = 0;

printf ("Please input a main string : \n"); //主串输入

scanf ("%s", str);

printf ("Please input a sub string : \n"); //字串输入

scanf ("%s", sub);

count = Substring(str, sub);

printf ("count = %d\n", count); //打印结果

return 0;

}