Largest Palindrome Product

Problem

Problem Link

A palindromic number reads the same both ways. The largest palindrome made from the product of two $2$-digit numbers is $9009=91\times 99$.

Find the largest palindrome made from the product of two $3$-digit numbers.

Solution

CodeCPP fileDownload

#include <algorithm>
#include <iostream>
#include <string>
 
bool palindrome(const std::string &s) {
  int n = s.length();
  for (int i = 0; i < n / 2; ++i) {
    if (s[i] != s[n - i - 1]) {
      return false;
    }
  }
  return true;
}
 
int main(void) {
  int ans = 0;
  for (int i = 100; i <= 999; ++i) {
    for (int j = 100; j <= 999; ++j) {
      int x = i * j;
      if (palindrome(std::to_string(x))) {
        ans = std::max(ans, x);
      }
    }
  }
  std::cout << ans << std::endl;
  return 0;
}