text:  int XXX(char * s){
      int i = 0;
      int count = 0, max = 0;
      int start = 0;
      int* index = (int*)malloc(128*sizeof(int)); 
      //int index[128] == 0;
      for(i; s[i] != '\0'; i++){
          if(index[s[i]] > start){
              count = i - start;
              max = count > max ? count : max;
              start = index[s[i]];  //不断刷新重复字符的位置
          }
          index[s[i]] = i+1;
      }
      count = i - start;
      max = count > max ? count : max;
      return max;
  }
  
  