Day04 AoC 2016

Day04.cpp

#include <algorithm>
#include <iostream>
#include <vector>
#include <chrono>

int main() {
  int index{-1};
  int sum{0};
  std::string line;
  auto timeStart = std::chrono::high_resolution_clock::now();
  while (std::getline(std::cin, line)) {
    int lastDash = line.find_last_of('-');
    int onlyBracket = line.find_last_of('[');
    std::string input{line.begin(), line.begin() + lastDash};
    std::string check{line.begin() + onlyBracket + 1, line.begin() + onlyBracket + 6};
    std::string sec{line.begin() + lastDash + 1, line.begin() + onlyBracket};
    int sector{std::stoi(sec)};
    if (index == -1) {
      for (char &c : input)
        c = (c=='-') ? c : ((c - 'a' + sector) % 26) + 'a';
      if (input.find("north") != std::string::npos)
        index = sector;
    }
    std::vector<std::pair<char, int>> s(26);
    for(int i{0}; i < 26; ++i)
      s[i] = {'a' + i, 0};
    for (char c : input)
      (c != '-') && ++s[c - 'a'].second;
    std::stable_sort(s.begin(), s.end(), [](const auto& p1, const auto& p2) {
        return p1.second > p2.second;
      });
    int i{0};
    while (i < 5 && s[i].first == check[i])
      ++i;
    sum += (i == 5) ? sector : 0;
  }
  auto timeStop = std::chrono::high_resolution_clock::now();
  std::cout << sum << '\n' << index << std::endl;
  std::cout << std::chrono::duration<double>{timeStop - timeStart}.count() << 's' << std::endl;
  return 0;
}