feat: Event 2018 day 12

Author: vuryss

core/src/main/java/com/vuryss/aoc/solutions/event2018/Day12.java

@@ -0,0 +1,112 @@
+package com.vuryss.aoc.solutions.event2018;
+
+import com.vuryss.aoc.solutions.SolutionInterface;
+import java.lang.Override;
+import java.lang.String;
+import java.lang.SuppressWarnings;
+import java.util.HashMap;
+import java.util.Map;
+
+@SuppressWarnings("unused")
+public class Day12 implements SolutionInterface {
+ @Override
+ public Map<String, String> part1Tests() {
+ return Map.of(
+ """
+ initial state: #..#.#..##......###...###
+ 
+ ...## => #
+ ..#.. => #
+ .#... => #
+ .#.#. => #
+ .#.## => #
+ .##.. => #
+ .#### => #
+ #.#.# => #
+ #.### => #
+ ##.#. => #
+ ##.## => #
+ ###.. => #
+ ###.# => #
+ ####. => #
+ """,
+ "325"
+ );
+ }
+
+ @Override
+ public Map<String, String> part2Tests() {
+ return Map.of();
+ }
+
+ @Override
+ public String part1Solution(String input, boolean isTest) {
+ return sumPots(input, 20);
+ }
+
+ @Override
+ public String part2Solution(String input, boolean isTest) {
+ return sumPots(input, 50_000_000_000L);
+ }
+
+ private String sumPots(String input, long generations) {
+ var parts = input.trim().split("\n\n");
+ var initialState = parts[0].split(" ")[2];
+ var rules = new HashMap<String, Character>();
+
+ for (var line: parts[1].split("\n")) {
+ var parts2 = line.split(" => ");
+ rules.put(parts2[0], parts2[1].charAt(0));
+ }
+
+ char[] state = new char[2000];
+ System.arraycopy(initialState.toCharArray(), 0, state, 1000, initialState.length());
+
+ int firstPlant = 1000, lastPlant = 1000 + initialState.length();
+ char[] newState;
+ long[] increments = new long[] { 999, 999, 999 };
+ long sum, lastSum = 0;
+
+ for (var i = 0L; i < generations; i++) {
+ newState = new char[2000];
+
+ for (var j = firstPlant - 2; j < lastPlant + 2; j++) {
+ var key = new StringBuilder();
+
+ for (var k = j - 2; k <= j + 2; k++) {
+ key.append(state[k] == '\0' ? '.' : state[k]);
+ }
+
+ newState[j] = rules.getOrDefault(key.toString(), '.');
+
+ if (newState[j] == '#') {
+ if (j < firstPlant) firstPlant = j;
+ if (j > lastPlant) lastPlant = j;
+ }
+ }
+
+ state = newState;
+ sum = sumPots(state, firstPlant, lastPlant);
+ increments[(int) i % 3] = sum - lastSum;
+ lastSum = sum;
+
+ if (increments[0] == increments[1] && increments[1] == increments[2]) {
+ return String.valueOf((generations - i - 1) * increments[0] + sum);
+ }
+ }
+
+ return String.valueOf(sumPots(state, firstPlant, lastPlant));
+ }
+
+ private long sumPots(char[] state, int firstPlant, int lastPlant) {
+ long sum = 0;
+
+ for (var i = firstPlant; i <= lastPlant; i++) {
+ if (state[i] == '#') {
+ sum += i - 1000;
+ }
+ }
+
+ return sum;
+ }
+}