Find the largest palindrome made from the product of two 3-digit numbers. http://projecteuler.net/problem=4

palindrome-as-product.cc

#include <stdio.h>
#include <string>

std::string positive_to_string(int num) {
  std::string s;
  while (num > 0) {
    s.push_back((char)('0' + (num % 10)));
    num /= 10;
  }
  return s;
}

bool is_palindrome(int num) {
  std::string str = positive_to_string(num);
  for (int s = 0; s < str.length() / 2; ++s) {
    if (str[s] != str[str.length() - s - 1]) {
      return false;
    }
  }
  return true;
}

int main() {
  int max_palindrome = 0;
  for (int i = 1; i < 1000; ++i) {
    for (int j = 1; j < 1000; ++j) {
      int p = i * j;
      if (is_palindrome(p)) {
        if (p > max_palindrome) {
          max_palindrome = p;
        }
      }
    }
  }
  printf("%d\n", max_palindrome);
  return 0;
}