C庫中的strstr()函數實現

#include <iostream>
#include <assert.h>
char* my_strstr(const char* str1, const char* str2)//在str1中找str2
{
	assert(str1);
	assert(str2);

	if (strlen(str1) < strlen(str2))
	{
		return NULL;
	}

	char* s1 = (char*)str1;
	char* s2 = (char*)str2;
	char* p = s1;

	while (*p)
	{
		s1 = p;
		s2 = (char*)str2;
		while (*s1 == *s2)
		{
			s1++;
			s2++;
		}
		if (*s2 == '\0')
		{
			return p;
		}
		p++;
	}

}