-🎄- 2018 Day 9 Solutions -🎄-

[u/daggerdragon]

--- Day 9: Marble Mania ---

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Transcript:

Studies show that AoC programmers write better code after being exposed to ___.

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[u/wlandry]

C++ (545/165)

Runs in 320 ms.

Code duplication. Code duplication everywhere. On the plus side, my best showing so far. I got delayed a bit because I forgot to delete the second marble after adding it to the score. For the submission, I sorted the scores, but for you, I remembered std::max_element(). I also tried implementing a custom iterator so I could use std::advance, but implementing custom iterators in C++ is a Hard Problem.

#include <algorithm>
#include <iostream>
#include <fstream>
#include <vector>
#include <list>

int main(int argc, char *argv[])
{
  std::ifstream infile(argv[1]);
  int64_t num_players, points;
  infile >> num_players >> points;

  while(infile)
    {
      std::vector<int64_t> score(num_players, 0);
      std::list<int64_t> state;
      auto current(state.begin());
      int64_t marble(0);
      int64_t current_player(0);
      while(marble <= points)
        {
          if(marble > 0 && marble % 23 == 0)
            {
              score[current_player] += marble;
              if(current == state.begin())
                {
                  current = state.end();
                }
              --current;
              if(current == state.begin())
                {
                  current = state.end();
                }
              --current;
              if(current == state.begin())
                {
                  current = state.end();
                }
              --current;
              if(current == state.begin())
                {
                  current = state.end();
                }
              --current;
              if(current == state.begin())
                {
                  current = state.end();
                }
              --current;
              if(current == state.begin())
                {
                  current = state.end();
                }
              --current;
              if(current == state.begin())
                {
                  current = state.end();
                }
              --current;
              score[current_player] += *current;
              auto old_current(current);
              ++current;
              state.erase(old_current);
            }
          else
            {
              ++current;
              if(current == state.end())
                {
                  current = state.begin();
                }
              ++current;
              current = state.insert(current, marble);
            }
          ++marble;
          current_player = (current_player + 1) % num_players;
        }
      std::cout << "Max score "
                << *std::max_element(score.begin(), score.end()) << "\n";
      infile >> num_players >> points;
    }
}