I should probably check this in at some point huh

src/day03/index.ts

@@ -0,0 +1,78 @@
+import run from "aocrunner"
+import { assert } from "console"
+
+const parseInput = (rawInput: string) => rawInput.trim().split("\n")
+
+function getPriority(c: string) {
+  const code = c.charCodeAt(0)
+  if (code >= 97) {
+    // "a"
+    return code - 96
+  }
+  return code - 65 /* "A" */ + 27
+}
+
+const part1 = (rawInput: string) => {
+  const input = parseInput(rawInput)
+  let total = 0
+  for (const rucksack of input) {
+    const [left, right] = [
+      rucksack.slice(0, rucksack.length / 2),
+      rucksack.slice(rucksack.length / 2),
+    ]
+    const leftItems = new Set(left.split(""))
+    const common = [...leftItems.values()].filter((c) => right.includes(c))
+    total += getPriority(common[0])
+  }
+  return total
+}
+
+const part2 = (rawInput: string) => {
+  const input = parseInput(rawInput)
+  let total = 0
+  const groupSize = 3
+  for (let g = 0; g < input.length; g += groupSize) {
+    const items = new Set(input[g])
+    for (let m = 1; m < groupSize; m++) {
+      for (const i of [...items.values()]) {
+        if (input[g + m].includes(i)) continue
+        else items.delete(i)
+      }
+    }
+    total += getPriority([...items.values()][0])
+  }
+  return total
+}
+
+run({
+  part1: {
+    tests: [
+      {
+        input: `vJrwpWtwJgWrhcsFMMfFFhFp
+jqHRNqRjqzjGDLGLrsFMfFZSrLrFZsSL
+PmmdzqPrVvPwwTWBwg
+wMqvLMZHhHMvwLHjbvcjnnSBnvTQFn
+ttgJtRGJQctTZtZT
+CrZsJsPPZsGzwwsLwLmpwMDw`,
+        expected: 157,
+      },
+    ],
+    solution: part1,
+  },
+  part2: {
+    tests: [
+      {
+        input: `vJrwpWtwJgWrhcsFMMfFFhFp
+jqHRNqRjqzjGDLGLrsFMfFZSrLrFZsSL
+PmmdzqPrVvPwwTWBwg
+wMqvLMZHhHMvwLHjbvcjnnSBnvTQFn
+ttgJtRGJQctTZtZT
+CrZsJsPPZsGzwwsLwLmpwMDw`,
+        expected: 70,
+      },
+    ],
+    solution: part2,
+  },
+  trimTestInputs: true,
+  onlyTests: false,
+})