advent-of-code-2020/day17/day17p1.cpp

117 lines
3.4 KiB
C++

#include <algorithm>
#include <fstream>
#include <iostream>
#include <map>
#include <set>
#include <string>
#include <tuple>
#include <vector>
#include "common.hpp"
using Position = std::tuple<int, int, int>;
using Board = std::map<Position, CellState>;
std::vector<std::string> readInput(const std::string &filename) {
std::vector<std::string> input;
std::string line;
std::ifstream file(filename);
while (std::getline(file, line)) {
input.push_back(line);
}
return input;
}
Board parseBoard(const std::vector<std::string> &input) {
Board board;
int rowCursor = 0;
for (auto rowIterator = input.cbegin(); rowIterator != input.cend(); (rowCursor++, ++rowIterator)) {
auto &line = *rowIterator;
int colCursor = 0;
for (auto colIterator = line.cbegin(); colIterator != line.cend(); (colCursor++, ++colIterator)) {
CellState state = *colIterator == ALIVE_CHAR ? ALIVE : DEAD;
Position position(rowCursor, colCursor, 0);
board.emplace(std::move(position), std::move(state));
}
}
return board;
}
int getNumAdjacentLiveNeighbors(const Board &board, int row, int col, int depth) {
int count = 0;
for (int dRow = -1; dRow <= 1; dRow++) {
for (int dCol = -1; dCol <= 1; dCol++) {
for (int dDepth = -1; dDepth <= 1; dDepth++) {
if (dRow == 0 && dCol == 0 && dDepth == 0) {
continue;
}
Position position(row + dRow, col + dCol, depth + dDepth);
if (board.find(position) == board.end()) {
continue;
}
count += (board.at(position) == ALIVE);
}
}
}
return count;
}
/**
* Get the range alive positions of each component
* @param board The board to check
* @return std::pair<Position, Position> The min and max of each component on the board
*/
std::pair<Position, Position> getRangeOnEachAxis(const Board &board) {
std::pair<int, int> rowRange = getMinMaxAlivePositionsForComponent<Position, 0>(board);
std::pair<int, int> colRange = getMinMaxAlivePositionsForComponent<Position, 1>(board);
std::pair<int, int> depthRange = getMinMaxAlivePositionsForComponent<Position, 2>(board);
return std::pair<Position, Position>(
Position(rowRange.first, colRange.first, depthRange.first),
Position(rowRange.second, colRange.second, depthRange.second));
}
int run(const std::vector<std::string> &input) {
Board board = parseBoard(input);
Board nextBoard = board;
for (int i = 0; i < CYCLE_COUNT; i++) {
auto ranges = getRangeOnEachAxis(board);
for (int row = std::get<0>(ranges.first) - 1; row <= std::get<0>(ranges.second) + 1; row++) {
for (int col = std::get<1>(ranges.first) - 1; col <= std::get<1>(ranges.second) + 1; col++) {
for (int depth = std::get<2>(ranges.first) - 1; depth <= std::get<2>(ranges.second) + 1; depth++) {
int aliveNeighbors = getNumAdjacentLiveNeighbors(board, row, col, depth);
Position position(row, col, depth);
CellState state = getOrDefault(board, DEAD, position);
if (aliveNeighbors != 2 && aliveNeighbors != 3) {
state = DEAD;
} else if (state == DEAD && aliveNeighbors == 3) {
state = ALIVE;
}
nextBoard[position] = state;
}
}
}
std::swap(nextBoard, board);
}
return std::count_if(
board.cbegin(), board.cend(), [](const std::pair<Position, CellState> &item) { return item.second == ALIVE; });
}
int main(int argc, char *argv[]) {
if (argc != 2) {
std::cerr << argv[0] << " <input_file>" << std::endl;
return 1;
}
auto input = readInput(argv[1]);
std::cout << run(input) << std::endl;
}