90 lines
2.7 KiB
Java
90 lines
2.7 KiB
Java
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import java.io.IOException;
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import java.math.BigInteger;
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import java.nio.file.Files;
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import java.nio.file.Path;
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import java.util.ArrayList;
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import java.util.List;
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import java.util.SortedSet;
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import java.util.TreeSet;
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class Solution {
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public static void main(String[] args) throws IOException {
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String contents = Files.readString(Path.of("input.txt"));
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String[] lines = contents.split("\n");
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List<Galaxy> galaxies = new ArrayList<Galaxy>();
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SortedSet<Integer> xs = new TreeSet<Integer>();
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SortedSet<Integer> ys = new TreeSet<Integer>();
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for (int x = 0; x < lines[0].length(); x++) {
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xs.add(x);
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}
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for (int y = 0; y < lines.length; y++) {
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ys.add(y);
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for (int x = 0; x < lines[y].length(); x++) {
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char c = lines[y].charAt(x);
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if (c == '#') {
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galaxies.add(new Galaxy(x, y));
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ys.remove(y);
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xs.remove(x);
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}
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}
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}
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// Part 1
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List<Galaxy> galaxiesPart1 = expandSpaces(galaxies, xs, ys, 2);
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int sum1 = 0;
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for (Galaxy g1 : galaxiesPart1) {
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for (Galaxy g2 : galaxiesPart1) {
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sum1 += g1.distance(g2);
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}
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}
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System.out.println(String.format("Part 1: %d", sum1 / 2));
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// Part 2
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List<Galaxy> galaxiesPart2 = expandSpaces(galaxies, xs, ys, 1000000);
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BigInteger sum2 = BigInteger.ZERO;
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for (Galaxy g1 : galaxiesPart2) {
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for (Galaxy g2 : galaxiesPart2) {
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int d = g1.distance(g2);
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sum2 = sum2.add(BigInteger.valueOf(d));
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}
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}
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System.out.println(String.format("Part 2: %d", sum2.divide(BigInteger.TWO)));
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}
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private static List<Galaxy> expandSpaces(Iterable<Galaxy> galaxies, Iterable<Integer> xs, Iterable<Integer> ys, int times) {
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List<Galaxy> newGalaxies = new ArrayList<Galaxy>();
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for (Galaxy g : galaxies) {
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int dx = 0;
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int dy = 0;
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for (Integer x : xs) {
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if (x < g.x) {
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dx += times - 1;
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} else {
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break;
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}
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}
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for (Integer y : ys) {
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if (y < g.y) {
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dy += times - 1;
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} else {
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break;
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}
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}
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newGalaxies.add(new Galaxy(g.x + dx, g.y + dy));
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}
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return newGalaxies;
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}
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}
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class Galaxy {
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public int x;
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public int y;
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public Galaxy(int x, int y) {
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this.x = x;
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this.y = y;
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}
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public int distance(Galaxy other) {
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return Math.abs(other.x - x) + Math.abs(other.y - y);
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}
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}
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