#include <stdio.h>#include <stdlib.h>#include <string.h> int main(int argc, const char * argv[]){  char str[] = "hello welcome to china/0"; //源字符串  printf("input a string:/n");         char str2[20];              //要查找的字符串  fgets(str2, 19, stdin);  char *res;  res = memchr(str, str2[0], strlen(str));  //根據要查找的字符串第一個字符，切割源字符串  if (res == NULL)  {    printf("find nothing.../n");    return 0;  }    int n;  while (1)  {    n = memcmp(res, str2, strlen(str2) - 1); //比較    if (n != 0)    {      if (strlen(res) <= strlen(str2))  //切割出的字符串小于要查找字符串的長度      {        printf("find nothing.../n");        return 0;      }      else      {         //根據要查找的第一個字符繼續切割        res = memchr(res + 1, str2[0], strlen(res));          if (res == NULL)        {          printf("find nothing.../n");          return 0;        }               }    }    else    { //如果n = 0，找到      printf("%s is found../n", str2);      return 0;    }  }}