problem 4

/*
A palindromic number reads the same both ways. The largest palindrome made from the x of two 2-digit numbers is 9009 = 91 × 99.

Find the largest palindrome made from the x of two 3-digit numbers.
*/

#include<iostream>
#include<string>
#include<vector>
#include <algorithm>    // std::reverse


using namespace std;

bool is_palindrome(int x){
  string num = std::to_string(x);
  std::reverse(num.begin(), num.end());
  if(num != to_string(x)){
    return false;
  }
  return true;
}

bool num(int x){
    int a,b,c,d,e,f;
	if(x<99999){

		a = x%10;
		b = (x%100 - a)/10;
		c= (x%1000 - b)/100;
		d = (x%10000 -c)/1000;
		e = (x%100000 - d)/10000;

		if((a == e) && (b == d)){
			return true;
		}else{
			return false;
		}

	}else{

		a = x%10;
		b = (x%100 - a)/10;
		c = (x%1000 - b)/100;
		d = (x%10000 - c)/1000;
		e= (x%100000 - d)/10000;
		f = (x%1000000 -e)/100000;

		if((a == f) && (b == e) && (c == d)){
			return true;
		}else{
			return false;
		}
	}
}

/*int find_max(const vector<int> nums){
  int max = nums[0];
  for(int num : nums){
    if(num > max){
      max = num;
    }
  }
  return max;
}
*/

int main(){
  vector<int> y;
  for( int i=100; i < 999; i++){
    for(int k=100; k < 999; k++){
      int j = k*i;
      if(is_palindrome(k*i)){
        y.push_back(j);
      }
    }
  }

  cout << *std::max_element(y.begin(), y.end()) << endl;
  return 0;
}