Solve 2024-01

2024/01/index.ts

@@ -0,0 +1,41 @@
+import { groupBy, sumArray } from '../../utils/array.ts';
+
+function splitColumnList(input: string) {
+  const regex = /^(\d*) {3}(\d*)$/gm;
+  const match = input.matchAll(regex);
+
+  const [first, second] = Array.from(
+    match,
+    (m) => [Number(m[1]), Number(m[2])] as [number, number]
+  ).reduce<[number[], number[]]>(
+    ([listA, listB], [a, b]) => {
+      listA.push(a);
+      listB.push(b);
+      return [listA, listB];
+    },
+    [[], []]
+  );
+  return { first, second };
+}
+
+export function solveFirst(input: string): number {
+  const { first, second } = splitColumnList(input);
+
+  first.sort();
+  second.sort();
+
+  const pairs = first.map((e, i) => Math.abs(e - second[i]));
+
+  return sumArray(pairs);
+}
+
+export function solveSecond(input: string): number {
+  const { first, second } = splitColumnList(input);
+
+  const right = groupBy(second, (e) => e);
+
+  const score = first.map(
+    (e) => e * (right.find((r) => r.key === e)?.elements?.length || 0)
+  );
+  return sumArray(score);
+}