#include <string>
#include <iostream>
#include <vector>
#include <chrono>

static const char CHARS[] = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";

static const int BENCHMARK_SIZE = 10000000;
static const int MAX_STRING_LENGTH = 50;

using time_point = std::chrono::high_resolution_clock::time_point;

void benchmark(std::vector<std::string> &list)
{
  std::chrono::high_resolution_clock::time_point t1 = std::chrono::high_resolution_clock::now();

  // force a copy of each string in the loop iteration
  for (const auto s : list) {
    static_cast<void>(s);
  }

  std::chrono::high_resolution_clock::time_point t2 = std::chrono::high_resolution_clock::now();
  const auto duration = std::chrono::duration_cast<std::chrono::milliseconds>(t2 - t1).count();
  std::cerr << list[0].length() << ',' << duration << '\n';
}


void generate_random_string(std::string &str, const int length)
{
  static float pi_number = 10 / 7;
  for (int i = 0; i < length; ++i) {
    str[i] = CHARS[(int)pi_number];
  }
  pi_number = (pi_number - int(pi_number)) * 10; // gives values of pi on and on.
}

int main()
{
  std::cerr << "length,time\n";
  std::vector<std::string> list;
  list.resize(BENCHMARK_SIZE);

  for (int length = 1; length <= MAX_STRING_LENGTH; length++) {
    for (int i = 0; i < BENCHMARK_SIZE; i++) {
      list[i].resize(length);
      generate_random_string(list[i], length);
    }
    benchmark(list);
  }

  return 0;
}