查找子串

#include <stdio.h>    const char *my_strstr(const char *str, const char *sub_str)  {      for(int i = 0; str[i] != '\0'; ++i)      {          int tem = i; //tem保留主串中子串的起始位置           int j = 0;          while(str[i++] == sub_str[j++])          {              if(sub_str[j] == '\0')              {                  return &str[tem];              }          }          i = tem;  //如果没返回，则i还是原来的位置    }      return NULL;  }    int main()  {      char *s = "1233345hello";      char *sub = "345";      printf("%s\n", my_strstr(s, sub));      return 0;  }