strstr函数实现

#include <stdio.h>#include <stdlib.h>#include <string.h>#include <assert.h>//在s1中查找s2，并返回s2在s1中第一次出现的位置char *strstr_bxy(const char *s1,const char *s2){assert(s1 != NULL && s2 != NULL);if(*s2 != '\0'){while(*s1 != '\0'){for(int n=0; *(s1+n) == *(s2+n); ++n){if(*(s2+n+1) == '\0'){return (char *)s1;}}s1++;}return NULL;}else{return (char *)s1;}}void main(){//输出NULL//const char *str1 = "abcdebcdf";//const char *str2 = "bd";//输出bcdebcdf//const char *str1 = "abcdebcdf";//const char *str2 = "bc";//触发断言，程序中止const char *str1 = "abcdebcdf";const char *str2 = NULL;char *c = strstr_bxy(str1,str2);if(c != NULL){puts(c);}else{printf("NULL\n");}}