AoC2025: day 3 part 2

Author: martapanc

2024-2025/src/2025/README.md

@@ -0,0 +1,16 @@
+# 🎄 Advent of Code 2025 🎄
+
+| Day                                            | Title                  | Code                   | Tests                        | Tags                                              | Difficulty | 
+|------------------------------------------------|------------------------|------------------------|------------------------------|---------------------------------------------------|------------|
+| [Day 1](https://adventofcode.com/2024/day/1)   | Historian Hysteria     | [code](day01/day01.ts) | [tests](day01/day01.test.ts) | num list comparison, abs value                    | 🧊         |
+| [Day 2](https://adventofcode.com/2024/day/2)   | Red-Nosed Reports      | [code](day02/day02.ts) | [tests](day02/day02.test.ts) | increasing/decreasing num list, deltas            | 🧊         |
+| [Day 3](https://adventofcode.com/2024/day/3)   | Mull It Over           | [code](day03/day03.ts) | [tests](day03/day03.test.ts) | regex, compiler                                   | 🧊         |
+| [Day 4](https://adventofcode.com/2024/day/4)   | Ceres Search           | [code](day04/day04.ts) | [tests](day04/day04.test.ts) | grid, crosswords                                  | 🧊🧊       |
+| [Day 5](https://adventofcode.com/2024/day/5)   | Print Queue            | [code](day05/day05.ts) | [tests](day05/day05.test.ts) | graph, topological sort, Kahn's                   | 🧊🧊🧊     |
+| [Day 6](https://adventofcode.com/2024/day/6)   | Guard Gallivant        | [code](day06/day06.ts) | [tests](day06/day06.test.ts) | grid, move & turn, detect loops                   | 🧊🧊       |
+| [Day 7](https://adventofcode.com/2024/day/7)   | Bridge Repair          | [code](day07/day07.ts) | [tests](day07/day07.test.ts) | equations, combos of + * \|\|, binary and ternary | 🧊🧊       |
+| [Day 8](https://adventofcode.com/2024/day/8)   | Resonant Collinearity  | [code](day08/day08.ts) | [tests](day08/day08.test.ts) | grid, Manhattan distance                          | 🧊🧊       |
+| [Day 9](https://adventofcode.com/2024/day/9)   | Disk Fragmented        | [code](day09/day09.ts) | [tests](day09/day09.test.ts) | disk fragmenting                                  | 🧊🧊🧊     |
+| [Day 10](https://adventofcode.com/2024/day/10) | Hoof It                | [code](day10/day10.ts) | [tests](day10/day10.test.ts) | topographic map, bfs, dfs                         | 🧊🧊       |
+| [Day 11](https://adventofcode.com/2024/day/11) | Plutonian Pebbles      | [code](day11/day11.ts) | [tests](day11/day11.test.ts) | list growing exponentially                        | 🧊🧊🧊     |
+| [Day 12](https://adventofcode.com/2024/day/12) | Garden Groups          | [code](day12/day12.ts) | [tests](day12/day12.test.ts) | flood fill; area, perimeter and sides             | 🧊🧊🧊     |

2024-2025/src/2025/day03/day03.test.ts

@@ -7,7 +7,7 @@ describe('2025 Day 3', () => {
     });
 
     test('Part 2', async () => {
-        // expect(await part2('testInput1')).toEqual(31);
-        // expect(await part2('input')).toEqual(29379307);
+        expect(await part2('testInput1')).toEqual(3121910778619);
+        expect(await part2('input')).toEqual(173577199527257);
     });
 });

2024-2025/src/2025/day03/day03.ts

@@ -6,7 +6,7 @@ export async function part1(inputFile: string) {
 }
 
 export async function part2(inputFile: string) {
-    return await day3(inputFile);
+    return await day3(inputFile, computeMaxJoltage12);
 }
 
 async function day3(inputFile: string, calcFn?: (batteryBanks: number[][]) => number) {
@@ -29,6 +29,26 @@ function getAllIndices(arr: number[], value: number): number[] {
     return indexes;
 }
 
+function largestKDigits(bank: number[], k: number): number {
+    const toRemove = bank.length - k;
+    const stack: number[] = [];
+    let removed = 0;
+
+    for (const digit of bank) {
+        while (removed < toRemove && stack.length > 0 && stack[stack.length - 1] < digit) {
+            stack.pop();
+            removed++;
+        }
+        stack.push(digit);
+    }
+
+    return Number(stack.slice(0, k).join(''));
+}
+
+function computeMaxJoltage12(batteryBanks: number[][]): number {
+    return batteryBanks.reduce((sum, bank) => sum + largestKDigits(bank, 12), 0);
+}
+
 function computeTotalOutputJoltage(batteryBanks: number[][]): number {
     let sum = 0;
     batteryBanks.forEach(batteryBank => {