Solved Day 21 part 2 (2015) - RPG Simulator 20XX

Author: SimonBaars

src/main/java/com/sbaars/adventofcode/year15/days/Day21.java

@@ -1,23 +1,202 @@
 package com.sbaars.adventofcode.year15.days;
 
 import com.sbaars.adventofcode.year15.Day2015;
+import java.util.*;
+import java.util.stream.Collectors;
 
 public class Day21 extends Day2015 {
- public Day21() {
- super(21);
- }
-
- public static void main(String[] args) {
- new Day21().printParts();
- }
-
- @Override
- public Object part1() {
- return "";
- }
-
- @Override
- public Object part2() {
- return "";
- }
+ private static final int PLAYER_HP = 100;
+ private static final List<Item> WEAPONS = Arrays.asList(
+ new Item("Dagger", 8, 4, 0),
+ new Item("Shortsword", 10, 5, 0),
+ new Item("Warhammer", 25, 6, 0),
+ new Item("Longsword", 40, 7, 0),
+ new Item("Greataxe", 74, 8, 0)
+ );
+ 
+ private static final List<Item> ARMOR = Arrays.asList(
+ new Item("Leather", 13, 0, 1),
+ new Item("Chainmail", 31, 0, 2),
+ new Item("Splintmail", 53, 0, 3),
+ new Item("Bandedmail", 75, 0, 4),
+ new Item("Platemail", 102, 0, 5)
+ );
+ 
+ private static final List<Item> RINGS = Arrays.asList(
+ new Item("Damage +1", 25, 1, 0),
+ new Item("Damage +2", 50, 2, 0),
+ new Item("Damage +3", 100, 3, 0),
+ new Item("Defense +1", 20, 0, 1),
+ new Item("Defense +2", 40, 0, 2),
+ new Item("Defense +3", 80, 0, 3)
+ );
+
+ private record Item(String name, int cost, int damage, int armor) {}
+ private record Character(int hp, int damage, int armor) {}
+ private record Equipment(Item weapon, Item armor, Item ring1, Item ring2) {
+ public int getTotalCost() {
+ return weapon.cost() + 
+ (armor != null ? armor.cost() : 0) + 
+ (ring1 != null ? ring1.cost() : 0) + 
+ (ring2 != null ? ring2.cost() : 0);
+ }
+ 
+ public int getTotalDamage() {
+ return weapon.damage() + 
+ (armor != null ? armor.damage() : 0) + 
+ (ring1 != null ? ring1.damage() : 0) + 
+ (ring2 != null ? ring2.damage() : 0);
+ }
+ 
+ public int getTotalArmor() {
+ return (armor != null ? armor.armor() : 0) + 
+ (ring1 != null ? ring1.armor() : 0) + 
+ (ring2 != null ? ring2.armor() : 0);
+ }
+ }
+
+ public Day21() {
+ super(21);
+ }
+
+ public static void main(String[] args) {
+ Day21 day = new Day21();
+ day.printParts();
+ new com.sbaars.adventofcode.network.Submit().submit(day.part2(), 2015, 21, 2);
+ }
+
+ @Override
+ public Object part1() {
+ Character boss = parseBoss();
+ return findMinGoldToWin(boss);
+ }
+
+ @Override
+ public Object part2() {
+ Character boss = parseBoss();
+ return findMaxGoldToLose(boss);
+ }
+
+ private Character parseBoss() {
+ List<String> lines = dayStream().collect(Collectors.toList());
+ int hp = Integer.parseInt(lines.get(0).split(": ")[1]);
+ int damage = Integer.parseInt(lines.get(1).split(": ")[1]);
+ int armor = Integer.parseInt(lines.get(2).split(": ")[1]);
+ return new Character(hp, damage, armor);
+ }
+
+ private int findMinGoldToWin(Character boss) {
+ int minGold = Integer.MAX_VALUE;
+ 
+ // Try all possible equipment combinations
+ for (Item weapon : WEAPONS) {
+ // Try with no armor and no rings
+ minGold = Math.min(minGold, tryEquipment(weapon, null, null, null, boss));
+ 
+ // Try with armor but no rings
+ for (Item armor : ARMOR) {
+ minGold = Math.min(minGold, tryEquipment(weapon, armor, null, null, boss));
+ }
+ 
+ // Try with one ring, no armor
+ for (Item ring1 : RINGS) {
+ minGold = Math.min(minGold, tryEquipment(weapon, null, ring1, null, boss));
+ }
+ 
+ // Try with two rings, no armor
+ for (int i = 0; i < RINGS.size(); i++) {
+ for (int j = i + 1; j < RINGS.size(); j++) {
+ minGold = Math.min(minGold, tryEquipment(weapon, null, RINGS.get(i), RINGS.get(j), boss));
+ }
+ }
+ 
+ // Try with armor and one ring
+ for (Item armor : ARMOR) {
+ for (Item ring1 : RINGS) {
+ minGold = Math.min(minGold, tryEquipment(weapon, armor, ring1, null, boss));
+ }
+ }
+ 
+ // Try with armor and two rings
+ for (Item armor : ARMOR) {
+ for (int i = 0; i < RINGS.size(); i++) {
+ for (int j = i + 1; j < RINGS.size(); j++) {
+ minGold = Math.min(minGold, tryEquipment(weapon, armor, RINGS.get(i), RINGS.get(j), boss));
+ }
+ }
+ }
+ }
+ 
+ return minGold;
+ }
+
+ private int tryEquipment(Item weapon, Item armor, Item ring1, Item ring2, Character boss) {
+ Equipment equipment = new Equipment(weapon, armor, ring1, ring2);
+ Character player = new Character(PLAYER_HP, equipment.getTotalDamage(), equipment.getTotalArmor());
+ 
+ return simulateFight(player, boss) ? equipment.getTotalCost() : Integer.MAX_VALUE;
+ }
+
+ private boolean simulateFight(Character player, Character boss) {
+ int playerDamagePerTurn = Math.max(1, player.damage() - boss.armor());
+ int bossDamagePerTurn = Math.max(1, boss.damage() - player.armor());
+ 
+ // Player goes first, so they need to kill the boss in equal or fewer turns
+ int turnsToKillBoss = (boss.hp() + playerDamagePerTurn - 1) / playerDamagePerTurn;
+ int turnsToKillPlayer = (player.hp() + bossDamagePerTurn - 1) / bossDamagePerTurn;
+ 
+ return turnsToKillBoss <= turnsToKillPlayer;
+ }
+
+ private int findMaxGoldToLose(Character boss) {
+ int maxGold = 0;
+ 
+ // Try all possible equipment combinations
+ for (Item weapon : WEAPONS) {
+ // Try with no armor and no rings
+ maxGold = Math.max(maxGold, tryEquipmentToLose(weapon, null, null, null, boss));
+ 
+ // Try with armor but no rings
+ for (Item armor : ARMOR) {
+ maxGold = Math.max(maxGold, tryEquipmentToLose(weapon, armor, null, null, boss));
+ }
+ 
+ // Try with one ring, no armor
+ for (Item ring1 : RINGS) {
+ maxGold = Math.max(maxGold, tryEquipmentToLose(weapon, null, ring1, null, boss));
+ }
+ 
+ // Try with two rings, no armor
+ for (int i = 0; i < RINGS.size(); i++) {
+ for (int j = i + 1; j < RINGS.size(); j++) {
+ maxGold = Math.max(maxGold, tryEquipmentToLose(weapon, null, RINGS.get(i), RINGS.get(j), boss));
+ }
+ }
+ 
+ // Try with armor and one ring
+ for (Item armor : ARMOR) {
+ for (Item ring1 : RINGS) {
+ maxGold = Math.max(maxGold, tryEquipmentToLose(weapon, armor, ring1, null, boss));
+ }
+ }
+ 
+ // Try with armor and two rings
+ for (Item armor : ARMOR) {
+ for (int i = 0; i < RINGS.size(); i++) {
+ for (int j = i + 1; j < RINGS.size(); j++) {
+ maxGold = Math.max(maxGold, tryEquipmentToLose(weapon, armor, RINGS.get(i), RINGS.get(j), boss));
+ }
+ }
+ }
+ }
+ 
+ return maxGold;
+ }
+
+ private int tryEquipmentToLose(Item weapon, Item armor, Item ring1, Item ring2, Character boss) {
+ Equipment equipment = new Equipment(weapon, armor, ring1, ring2);
+ Character player = new Character(PLAYER_HP, equipment.getTotalDamage(), equipment.getTotalArmor());
+ 
+ return simulateFight(player, boss) ? 0 : equipment.getTotalCost();
+ }
 }