以下程式碼亟待改進

#include <iostream>
#include <string>
using namespace std;

bool check_range(string s){
  int i = stoi(s);
  if (i >= 0 && i <= 255)
    return true;
  return false;
}

void find_valid(string s, string remain, int *length, int count){
  if (count == 4){
    if (remain.size() != 0)
      return;
    cout << s.substr(0, length[0]) << '.' <<  s.substr(length[0], length[1]) << '.' << 
      s.substr(length[0] + length[1], length[2]) << '.' << s.substr(length[0] + length[1] + length[2], length[3]) << endl;
  }

  for (int i = 1; i <= 3; ++i){
    if (remain.size() >= i && check_range(remain.substr(0, i))){
      length[count] = i;
      find_valid(s, remain.substr(i), length, count + 1);
    }
    else{
      break;
    }
  }
}


int main(){
  string s = "25525510215";
  //255.255.10.215
  //255.255.102.15

  int length[4] = {0};
  find_valid(s, s, length, 0);

  int ttt = 0;
  return 0;
}