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1 | 1 | package com.sbaars.adventofcode.year15.days; |
2 | 2 |
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3 | 3 | import com.sbaars.adventofcode.year15.Day2015; |
| 4 | +import java.util.*; |
| 5 | +import java.util.stream.Collectors; |
| 6 | +import java.util.stream.IntStream; |
4 | 7 |
|
5 | 8 | public class Day18 extends Day2015 { |
6 | | - public Day18() { |
7 | | - super(18); |
8 | | - } |
9 | | - |
10 | | - public static void main(String[] args) { |
11 | | - new Day18().printParts(); |
12 | | - } |
13 | | - |
14 | | - @Override |
15 | | - public Object part1() { |
16 | | - return ""; |
17 | | - } |
18 | | - |
19 | | - @Override |
20 | | - public Object part2() { |
21 | | - return ""; |
22 | | - } |
| 9 | + |
| 10 | + private static final int GRID_SIZE = 100; |
| 11 | + private static final int STEPS = 100; |
| 12 | + private boolean[][] grid; |
| 13 | + |
| 14 | + public Day18() { |
| 15 | + super(18); |
| 16 | + parseInput(); |
| 17 | + } |
| 18 | + |
| 19 | + public static void main(String[] args) { |
| 20 | + Day18 day = new Day18(); |
| 21 | + day.printParts(); |
| 22 | + new com.sbaars.adventofcode.network.Submit().submit(day.part1(), 2015, 18, 1); |
| 23 | + } |
| 24 | + |
| 25 | + private void parseInput() { |
| 26 | + grid = new boolean[GRID_SIZE][GRID_SIZE]; |
| 27 | + String[] lines = day().split("\n"); |
| 28 | + for (int i = 0; i < GRID_SIZE; i++) { |
| 29 | + String line = lines[i].trim(); |
| 30 | + for (int j = 0; j < GRID_SIZE; j++) { |
| 31 | + grid[i][j] = line.charAt(j) == '#'; |
| 32 | + } |
| 33 | + } |
| 34 | + } |
| 35 | + |
| 36 | + @Override |
| 37 | + public Object part1() { |
| 38 | + boolean[][] currentGrid = copyGrid(grid); |
| 39 | + for (int step = 0; step < STEPS; step++) { |
| 40 | + currentGrid = nextStep(currentGrid); |
| 41 | + } |
| 42 | + return countLights(currentGrid); |
| 43 | + } |
| 44 | + |
| 45 | + @Override |
| 46 | + public Object part2() { |
| 47 | + return 0; // Implement in next part |
| 48 | + } |
| 49 | + |
| 50 | + private boolean[][] nextStep(boolean[][] currentGrid) { |
| 51 | + boolean[][] newGrid = new boolean[GRID_SIZE][GRID_SIZE]; |
| 52 | + |
| 53 | + for (int i = 0; i < GRID_SIZE; i++) { |
| 54 | + for (int j = 0; j < GRID_SIZE; j++) { |
| 55 | + int neighbors = countNeighbors(currentGrid, i, j); |
| 56 | + if (currentGrid[i][j]) { |
| 57 | + newGrid[i][j] = neighbors == 2 || neighbors == 3; |
| 58 | + } else { |
| 59 | + newGrid[i][j] = neighbors == 3; |
| 60 | + } |
| 61 | + } |
| 62 | + } |
| 63 | + |
| 64 | + return newGrid; |
| 65 | + } |
| 66 | + |
| 67 | + private int countNeighbors(boolean[][] grid, int row, int col) { |
| 68 | + return (int) IntStream.rangeClosed(row - 1, row + 1) |
| 69 | + .filter(r -> r >= 0 && r < GRID_SIZE) |
| 70 | + .flatMap(r -> IntStream.rangeClosed(col - 1, col + 1) |
| 71 | + .filter(c -> c >= 0 && c < GRID_SIZE) |
| 72 | + .filter(c -> !(r == row && c == col)) |
| 73 | + .filter(c -> grid[r][c])) |
| 74 | + .count(); |
| 75 | + } |
| 76 | + |
| 77 | + private boolean[][] copyGrid(boolean[][] original) { |
| 78 | + boolean[][] copy = new boolean[GRID_SIZE][GRID_SIZE]; |
| 79 | + for (int i = 0; i < GRID_SIZE; i++) { |
| 80 | + copy[i] = Arrays.copyOf(original[i], GRID_SIZE); |
| 81 | + } |
| 82 | + return copy; |
| 83 | + } |
| 84 | + |
| 85 | + private long countLights(boolean[][] grid) { |
| 86 | + return Arrays.stream(grid) |
| 87 | + .flatMap(row -> IntStream.range(0, row.length).mapToObj(i -> row[i])) |
| 88 | + .filter(light -> light) |
| 89 | + .count(); |
| 90 | + } |
23 | 91 | } |
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