#include <algorithm>
#include <chrono>
#include <iostream>
#include <random>
#include <string>
#include <unordered_map>
#include <vector>

using namespace std;
using namespace std::chrono;

int N = 1000000; // 1,000,000 tries
int L = 20;      // string length

string random_string(size_t length) {
  static const string chars =
    "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";

  static random_device rd;
  static mt19937 gen(rd());

  uniform_int_distribution<> dist(0, chars.size() - 1);

  string s;

  for (size_t i = 0; i < length; i++) {
    s += chars[dist(gen)];
  }

  return s;
}

void test_array(int length) {
  std::unordered_map<std::string, int> hash_map;
  hash_map.reserve(length * 2); // Reserve more to avoid rehashing
  std::vector<std::pair<std::string, int>> array;
  array.reserve(length);

  vector<string> keys;

  for (int i = 0; i < length; ++i) {
    string key = random_string(L);

    keys.push_back(key);

    hash_map[key] = i;
    array.emplace_back(key, i);
  }

  auto start = std::chrono::high_resolution_clock::now();
  for (int i = 0; i < N; ++i) {
    string &key = keys[i % length];

    auto it = hash_map.find(key);

    volatile int value = it->second;
    (void)value;
  }
  auto end = std::chrono::high_resolution_clock::now();
  auto hash_duration = std::chrono::duration_cast<std::chrono::milliseconds>(end - start).count();

  start = std::chrono::high_resolution_clock::now();
  for (int i = 0; i < N; ++i) {
    string &key = keys[i % length];

    auto it = std::find_if(array.begin(), array.end(), [&key](const auto &pair) {
      return pair.first == key;
    });

    volatile int value = it->second;
    (void)value;
  }
  end = std::chrono::high_resolution_clock::now();
  auto array_duration = std::chrono::duration_cast<std::chrono::milliseconds>(end - start).count();

  std::cout << length << "," << hash_duration << "," << array_duration << "\n";
}

int main() {
  std::cout << "elements,hash,array\n";

  for (int length = 1; length <= 10; length++)
    test_array(length);
  for (int length = 10; length <= 100; length += 10)
    test_array(length);
  for (int length = 100; length <= 1000; length += 100)
    test_array(length);

  return 0;
}