#include <array>
#include <chrono>
#include <cstdlib>
#include <ctime>
#include <iostream>

using namespace std::chrono;
using namespace std;

int main() {
  // Setup
  int sum = 0;
  const std::size_t arrLength = 4000 + 4000 * 4000;
  int *arr = new int[arrLength];

  for (size_t i = 0; i < arrLength; i++) {
    int value = rand() % arrLength;
    arr[i] = value;
  }

  // Algorithm #1
  auto start = high_resolution_clock::now();

  for (int x = 0; x < 4000; ++x) {
    for (int y = 0; y < 4000; ++y) {
      sum += arr[x * 4000 + y];
    }
  }

  auto stop = high_resolution_clock::now();
  auto duration = duration_cast<microseconds>(stop - start);

  cout << "Finished after " << duration.count() << endl;

  // Algorithm #2
  start = high_resolution_clock::now();

  for (int y = 0; y < 4000; ++y) {
    for (int x = 0; x < 4000; ++x) {
      sum += arr[x + 4000 * y];
    }
  }

  stop = high_resolution_clock::now();
  duration = duration_cast<microseconds>(stop - start);

  cout << "Finished after " << duration.count() << endl;

  return 0;
}