feat: 2025 Day 3

Author: mfulton26

2025/day/3/part/1/solve.test.ts

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+import solve from "./solve.ts";
+
+import { assertEquals } from "@std/assert";
+
+Deno.test("example", () => {
+  const input = `\
+987654321111111
+811111111111119
+234234234234278
+818181911112111`;
+
+  assertEquals(solve(input), 357);
+});

2025/day/3/part/1/solve.ts

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+export default function solve(input: string) {
+  const banks = input.split("\n").map((line) => Array.from(line, Number));
+  let sum = 0;
+  for (const bank of banks) {
+    const max = Math.max(...bank.slice(0, -1));
+    const indexOfMax = bank.findIndex((value) => value === max);
+    sum += max * 10 + Math.max(...bank.slice(indexOfMax + 1));
+  }
+  return sum;
+}

2025/day/3/part/2/solve.test.ts

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+import solve from "./solve.ts";
+
+import { assertEquals } from "@std/assert";
+
+Deno.test("example", () => {
+  const input = `\
+987654321111111
+811111111111119
+234234234234278
+818181911112111`;
+
+  assertEquals(solve(input), 3121910778619);
+});

2025/day/3/part/2/solve.ts

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+export default function solve(input: string) {
+  const banks = input.split("\n").map((line) => Array.from(line, Number));
+  let sum = 0;
+  for (let bank of banks) {
+    const digits = [Math.max(...bank.slice(0, -11))];
+    while (digits.length < 12) {
+      bank = bank.slice(bank.indexOf(digits[digits.length - 1]) + 1);
+      digits.push(Math.max(...bank.slice(0, bank.length - 11 + digits.length)));
+    }
+    sum += +digits.join("");
+  }
+  return sum;
+}