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feat: Day 24: Immune System Simulator 20XX (part 2)
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‎.github/badges/completion.json

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{
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"schemaVersion": 1,
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"label": "completion",
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"message": "37/50",
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"message": "41/50",
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"color": "yellow"
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}

‎day-24-immune-system-simulator-20xx/README.md

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@@ -187,5 +187,171 @@ In the example above, the winning army ends up with `782 + 4434 = 5216 units`.
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You scan the reindeer's condition (your puzzle input); the white-bearded man looks nervous. As it stands now, **how many units would the winning army have**?
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## Part Two
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Things aren't looking good for the reindeer. The man asks whether more milk and cookies would help you think.
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If only you could give the reindeer's immune system a boost, you might be able to change the outcome of the combat.
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A **boost** is an integer increase in immune system units' attack damage. For example, if you were to boost the above example's immune system's units by `1570`, the armies would instead look like this:
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```
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Immune System:
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17 units each with 5390 hit points (weak to radiation, bludgeoning) with
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an attack that does 6077 fire damage at initiative 2
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989 units each with 1274 hit points (immune to fire; weak to bludgeoning,
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slashing) with an attack that does 1595 slashing damage at initiative 3
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Infection:
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801 units each with 4706 hit points (weak to radiation) with an attack
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that does 116 bludgeoning damage at initiative 1
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4485 units each with 2961 hit points (immune to radiation; weak to fire,
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cold) with an attack that does 12 slashing damage at initiative 4
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With this boost, the combat proceeds differently:
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```
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With this boost, the combat proceeds differently:
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```
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Immune System:
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Group 2 contains 989 units
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Group 1 contains 17 units
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Infection:
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Group 1 contains 801 units
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Group 2 contains 4485 units
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Infection group 1 would deal defending group 2 185832 damage
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Infection group 1 would deal defending group 1 185832 damage
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Infection group 2 would deal defending group 1 53820 damage
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Immune System group 2 would deal defending group 1 1577455 damage
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Immune System group 2 would deal defending group 2 1577455 damage
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Immune System group 1 would deal defending group 2 206618 damage
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Infection group 2 attacks defending group 1, killing 9 units
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Immune System group 2 attacks defending group 1, killing 335 units
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Immune System group 1 attacks defending group 2, killing 32 units
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Infection group 1 attacks defending group 2, killing 84 units
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```
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```
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Immune System:
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Group 2 contains 905 units
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Group 1 contains 8 units
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Infection:
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Group 1 contains 466 units
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Group 2 contains 4453 units
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Infection group 1 would deal defending group 2 108112 damage
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Infection group 1 would deal defending group 1 108112 damage
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Infection group 2 would deal defending group 1 53436 damage
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Immune System group 2 would deal defending group 1 1443475 damage
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Immune System group 2 would deal defending group 2 1443475 damage
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Immune System group 1 would deal defending group 2 97232 damage
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Infection group 2 attacks defending group 1, killing 8 units
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Immune System group 2 attacks defending group 1, killing 306 units
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Infection group 1 attacks defending group 2, killing 29 units
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```
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```
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Immune System:
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Group 2 contains 876 units
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Infection:
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Group 2 contains 4453 units
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Group 1 contains 160 units
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Infection group 2 would deal defending group 2 106872 damage
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Immune System group 2 would deal defending group 2 1397220 damage
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Immune System group 2 would deal defending group 1 1397220 damage
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Infection group 2 attacks defending group 2, killing 83 units
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Immune System group 2 attacks defending group 2, killing 427 units
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```
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After a few fights...
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```
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Immune System:
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Group 2 contains 64 units
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Infection:
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Group 2 contains 214 units
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Group 1 contains 19 units
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Infection group 2 would deal defending group 2 5136 damage
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Immune System group 2 would deal defending group 2 102080 damage
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Immune System group 2 would deal defending group 1 102080 damage
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Infection group 2 attacks defending group 2, killing 4 units
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Immune System group 2 attacks defending group 2, killing 32 units
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```
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```
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Immune System:
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Group 2 contains 60 units
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Infection:
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Group 1 contains 19 units
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Group 2 contains 182 units
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Infection group 1 would deal defending group 2 4408 damage
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Immune System group 2 would deal defending group 1 95700 damage
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Immune System group 2 would deal defending group 2 95700 damage
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Immune System group 2 attacks defending group 1, killing 19 units
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```
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```
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Immune System:
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Group 2 contains 60 units
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Infection:
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Group 2 contains 182 units
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Infection group 2 would deal defending group 2 4368 damage
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Immune System group 2 would deal defending group 2 95700 damage
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Infection group 2 attacks defending group 2, killing 3 units
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Immune System group 2 attacks defending group 2, killing 30 units
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```
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After a few more fights...
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```
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Immune System:
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Group 2 contains 51 units
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Infection:
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Group 2 contains 40 units
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Infection group 2 would deal defending group 2 960 damage
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Immune System group 2 would deal defending group 2 81345 damage
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Infection group 2 attacks defending group 2, killing 0 units
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Immune System group 2 attacks defending group 2, killing 27 units
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```
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```
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Immune System:
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Group 2 contains 51 units
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Infection:
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Group 2 contains 13 units
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Infection group 2 would deal defending group 2 312 damage
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Immune System group 2 would deal defending group 2 81345 damage
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Infection group 2 attacks defending group 2, killing 0 units
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Immune System group 2 attacks defending group 2, killing 13 units
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```
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```
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Immune System:
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Group 2 contains 51 units
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Infection:
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No groups remain.
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```
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This boost would allow the immune system's armies to win! It would be left with **`51`** units.
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You don't even know **how** you could boost the reindeer's immune system or what effect it might have, so you need to be cautious and find the **smallest boost** that would allow the immune system to win.
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**How many units does the immune system have left** after getting the smallest boost it needs to win?
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## References
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- https://adventofcode.com/2018/day/24

‎day-24-immune-system-simulator-20xx/immune-system.js

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@@ -175,5 +175,3 @@ module.exports = (input) => {
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.find((army) => !army.isDead).groups
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.reduce((units, group) => units + group.units, 0);
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};
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// 18341 too high

‎day-24-immune-system-simulator-20xx/immune-system2.js

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const PRINT_COMBAT_TEXT = false;
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function print () {
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if (PRINT_COMBAT_TEXT) {
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const args = Array.from(arguments);
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console.log(...args);
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}
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}
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const parseArmyInformation = (input) => {
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return input
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.split('\n\n')
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.map((army, armyIndex) => {
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const armyName = armyIndex === 0 ? 'Immune System' : 'Infection';
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const groups = army
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.split('\n')
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.slice(1)
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.map((line, groupIndex) => {
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const parts = /(\d+) units each with (\d+) hit points .*with an attack that does (\d+) (\w+) damage at initiative (\d+)/.exec(line.trim());
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const modifiers = /\((.*)\)/.exec(line.trim());
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const tags = modifiers
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? modifiers[1].split(';').reduce((map, definition) => {
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/weak to/.test(definition)
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? map.set('weaknesses', new Set(/weak to (.*)/.exec(definition)[1].split(', ')))
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: map.set('immunities', new Set(/immune to (.*)/.exec(definition)[1].split(', ')));
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return map;
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}, new Map())
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: new Map();
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return {
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armyName,
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number: groupIndex + 1,
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units: +parts[1],
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hitPoints: +parts[2],
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weaknesses: tags.get('weaknesses') || new Set(),
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immunities: tags.get('immunities') || new Set(),
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attackDamage: +parts[3],
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attackType: parts[4],
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initiative: +parts[5],
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get effectivePower() {
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return this.units * this.attackDamage;
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},
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get isDead() {
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return this.units <= 0;
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},
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};
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});
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return {
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name: armyName,
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groups,
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get isDead() {
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return this.groups.every((group) => group.isDead);
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},
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};
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});
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};
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const printArmyStatus = (army) => {
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print(`${army.name}:`);
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army.groups.every((group) => group.isDead)
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? print('No groups remain.')
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: army.groups.forEach((group) => !group.isDead && print(`Group ${group.number} contains ${group.units} units`));
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};
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const attackerSelectionSort = (a, b) => {
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return b.effectivePower - a.effectivePower === 0
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? b.initiative - a.initiative
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: b.effectivePower - a.effectivePower;
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};
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const effectiveDamage = (attacker, defender) => {
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const { effectivePower, attackType } = attacker;
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return (defender.weaknesses.has(attackType) ? 2 : (defender.immunities.has(attackType) ? 0 : 1)) * effectivePower;
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};
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const targetSelectionSort = (a, b) => {
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return b.damage - a.damage === 0
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? b.group.effectivePower - a.group.effectivePower === 0
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? b.group.initiative - a.group.initiative
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: b.group.effectivePower - a.group.effectivePower
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: b.damage - a.damage;
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};
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const targetSelectionPhase = (attackers, defenders) => {
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const sortedAttackers = [...attackers.groups].filter((group) => !group.isDead).sort(attackerSelectionSort);
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const availableDefenders = [...defenders.groups].filter((group) => !group.isDead);
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const plannedAttacks = [];
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sortedAttackers.forEach((attackingGroup) => {
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const effectiveDamageOnDefenders = availableDefenders.map((defendingGroup) => {
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return {
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damage: effectiveDamage(attackingGroup, defendingGroup),
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group: defendingGroup,
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};
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});
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// print target selection phase
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effectiveDamageOnDefenders.forEach(({ damage, group }) => {
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print(`${attackers.name} group ${attackingGroup.number} would deal defending group ${group.number} ${damage} damage`);
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});
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if (!effectiveDamageOnDefenders.length) {
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return;
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}
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const selectedTarget = effectiveDamageOnDefenders.sort(targetSelectionSort)[0];
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if (selectedTarget.damage === 0) {
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return;
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}
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plannedAttacks.push({
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attackingGroup,
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defendingGroup: selectedTarget.group,
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});
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const selectedDefenderIndex = availableDefenders.findIndex(({ number }) => selectedTarget.group.number === number);
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availableDefenders.splice(selectedDefenderIndex, 1);
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});
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return plannedAttacks;
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};
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const attackingPhaseSort = (a, b) => {
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return b.attackingGroup.initiative - a.attackingGroup.initiative;
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};
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const attackingPhase = (plannedAttacks) => {
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const sortedAttackingOrder = plannedAttacks.sort(attackingPhaseSort);
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for (let i = 0; i < sortedAttackingOrder.length; i++) {
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const { attackingGroup, defendingGroup } = sortedAttackingOrder[i];
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const damage = effectiveDamage(attackingGroup, defendingGroup);
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const killedUnits = Math.min(Math.floor(damage / defendingGroup.hitPoints), defendingGroup.units);
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print(`${attackingGroup.armyName} group ${attackingGroup.number} attacks defending group ${defendingGroup.number}, killing ${killedUnits} units`);
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defendingGroup.units -= killedUnits;
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}
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};
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const simulate = (armies) => {
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while (!armies[0].isDead && !armies[1].isDead) {
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printArmyStatus(armies[0]);
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printArmyStatus(armies[1]);
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print('');
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// target selection phase
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const plannedAttacks = [
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...targetSelectionPhase(armies[1], armies[0]),
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...targetSelectionPhase(armies[0], armies[1]),
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];
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// halt if opposing groups are immune to each other
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if (!plannedAttacks.length) {
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return [false, 0];
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}
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print('');
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// attacking phase
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attackingPhase(plannedAttacks);
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print('');
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}
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printArmyStatus(armies[0]);
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printArmyStatus(armies[1]);
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return [
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!armies[0].isDead,
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armies[0].groups.reduce((units, group) => units + group.units, 0),
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];
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};
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const boost = (army, amount) => {
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army.groups.forEach((group) => group.attackDamage += amount);
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};
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module.exports = (input) => {
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let appliedBoost = 1;
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let minimumBoost = appliedBoost;
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let maximumBoost = Infinity;
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while (appliedBoost <= maximumBoost) {
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const armies = parseArmyInformation(input);
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boost(armies[0], appliedBoost);
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const [success, immuneSystemUnitsLeft] = simulate(armies);
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if (!success) {
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minimumBoost = appliedBoost;
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appliedBoost = maximumBoost === Infinity
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? appliedBoost *= 2
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: Math.floor((maximumBoost - minimumBoost) / 2 + 1) + minimumBoost;
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} else if (appliedBoost < maximumBoost) {
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maximumBoost = appliedBoost;
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appliedBoost = Math.floor((maximumBoost - minimumBoost) / 2 + 1) + minimumBoost;
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} else {
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return immuneSystemUnitsLeft;
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}
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}
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};

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