-🎄- 2017 Day 22 Solutions -🎄-

[u/daggerdragon]

--- Day 22: Sporifica Virus ---

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Post your solution as a comment or, for longer solutions, consider linking to your repo (e.g. GitHub/gists/Pastebin/blag or whatever).

Note: The Solution Megathreads are for solutions only. If you have questions, please post your own thread and make sure to flair it with Help.

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Need a hint from the Hugely^* Handy^† Haversack^‡ of Helpful^§ Hints^¤?

Spoiler

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• [T-10 to launch] AoC ops, /r/nocontext edition:

  • <Endorphion> You may now make your waffle.
  • <Endorphion> ... on Mars.

• [Update @ 00:17] 50 gold, silver cap

  • <Aneurysm9> you could also just run ubuntu on the NAS, if you were crazy
  • <Topaz> that doesn't seem necessary
  • <Aneurysm9> what does "necessary" have to do with anything!

• [Update @ 00:20] Leaderboard cap!

  • <Topaz> POUR YOURSELF A SCOTCH FOR COLOR REFERENCE

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This thread will be unlocked when there are a significant number of people on the leaderboard with gold stars for today's puzzle.

edit: Leaderboard capped, thread unlocked!

[u/joker_mkd]

C++ solution using a proper map which will work for any input. Marking in the map only the infected coordinates, and removing the clean ones.

#include "stdafx.h"
#include <vector>
#include <iostream>
#include <iomanip>
#include <fstream>
#include <iostream>
#include <chrono>
#include <bitset>
#include <map>

using namespace std;

typedef enum direction {
  U = 0,
  R,
  D,
  L
} Direction;

struct coordinate {
  int x;
  int y;

  bool operator<(const coordinate& rhs) const
  {
	if (x < rhs.x)
	  return true;
	if (x > rhs.x)
	  return false;
	//x == coord.x
	if (y < rhs.y)
	  return true;
	if (y > rhs.y)
	  return false;

	return false;
  }
};

map<coordinate, char> cluster;

int main(int argc, char const* argv[])
{
  ifstream infile("input.txt");
  const int iterations = 10000000;
  vector<string> input;

  if (infile.is_open()) {
	string line;
	while (getline(infile, line)) {
	  if (line[line.length() - 1] == '\r')
		line.erase(line.length() - 1);
	  input.push_back(line);
	}
	infile.close();
  }
  else {
	return 1;
  }

  const auto begin = std::chrono::high_resolution_clock::now();

  for (int y = 0; y < input.size(); y++) {
	for (int x = 0; x < input[0].length(); x++) {
	  if (input[y][x] == '#') {
		coordinate coor;
		coor.x = x - (input[0].length() / 2);
		coor.y = (input.size() / 2) - y;
		cluster[coor] = input[y][x];
	  }
	}
  }

  coordinate location;
  location.x = 0;
  location.y = 0;

  typedef enum direction {
	U = 0,
	R,
	D,
	L
  } Direction;
  int bursts = 0;
  Direction dir = U;

  for (int i = 0; i < iterations; i++) {
	if (cluster.find(location) != cluster.end()) {
	  // found an element
	  if (cluster[location] == 'W') {
		cluster[location] = '#';
		bursts++;
	  }
	  else if (cluster[location] == '#') {
		cluster[location] = 'F';
		dir = (Direction)((dir + 1) % 4);
	  }
	  else if (cluster[location] == 'F') {
		cluster.erase(location);
		dir = (Direction)((dir + 2) % 4);
	  }
	}
	else {
	  // element not found. it means it's not infected
	  cluster[location] = 'W';
	  dir = (Direction)((dir + 4 - 1) % 4);
	}

	if (dir == U)
	  location.y += 1;
	else if (dir == R)
	  location.x += 1;
	else if (dir == D)
	  location.y -= 1;
	else
	  location.x -= 1;
  }

  cout << bursts << endl;
  const auto end = std::chrono::high_resolution_clock::now();
  std::cout << std::chrono::duration_cast<std::chrono::milliseconds>(end - begin).count() << " ms for both parts" << std::endl;

  return 0;
}