C++ - 实现strstr函数

/*函数名: strstr功能：找出字符串str2在字符串str1中第一次出现的位置（不包括str2的串结束符）。返回值：若找到，返回指向该位置的指针；否则，返回空指针。*/#include <iostream>#define NULL 0using namespace std;char* myStrstr(const char* s1, const char* s2){if (*s2){while (*s1){for (int i = 0; *(s1 + i) == *(s2 + i); i++){if (!*(s2 + i + 1)){return (char*)s1;}}s1++;}return NULL;}else{return (char*)s1;}}int main(){char s1[20] = "453456789123456788";char s2[6] = "34567";char* s = myStrstr(s1, s2);cout << s << endl;return 0;}// Output:/*3456789123456788*/