Solve 2024-10

2024/10/index.ts

@@ -0,0 +1,98 @@
+import { sumArray, unique } from '../../utils/array.ts';
+import {
+  type Coordinates,
+  findCoordsOfDigit,
+  getAdjacent,
+  isCoordinateEqual
+} from '../../utils/coordinates.ts';
+
+export function getScoreOfHead(
+  rows: string[],
+  startX: number,
+  startY: number,
+  startDigit = 0
+): Coordinates {
+  if (startDigit >= 9) {
+    return [[startX, startY]];
+  }
+
+  const top = rows[startY - 1]?.[startX];
+  const right = rows[startY]?.[startX + 1];
+  const down = rows[startY + 1]?.[startX];
+  const left = rows[startY]?.[startX - 1];
+
+  let found: Coordinates = [];
+  const lookFor = startDigit + 1;
+
+  if (top && Number(top) === lookFor) {
+    found.push(...getScoreOfHead(rows, startX, startY - 1, lookFor));
+  }
+  if (right && Number(right) === lookFor) {
+    found.push(...getScoreOfHead(rows, startX + 1, startY, lookFor));
+  }
+  if (down && Number(down) === lookFor) {
+    found.push(...getScoreOfHead(rows, startX, startY + 1, lookFor));
+  }
+  if (left && Number(left) === lookFor) {
+    found.push(...getScoreOfHead(rows, startX - 1, startY, lookFor));
+  }
+
+  return found;
+}
+
+export function solveFirst(input: string): number {
+  const rows = input.split('\n');
+
+  const trailHeads = findCoordsOfDigit(rows, '0');
+
+  const scores = trailHeads.map(
+    ([startX, startY]) =>
+      getScoreOfHead(rows, startX, startY).filter(unique(isCoordinateEqual))
+        .length
+  );
+
+  return sumArray(scores);
+}
+
+export function getRatingOfHead(
+  rows: string[],
+  startX: number,
+  startY: number,
+  startDigit = 0
+): Coordinates[] {
+  if (startDigit >= 9) {
+    return [[[startX, startY]]];
+  }
+
+  const { top, right, left, down } = getAdjacent(rows, startX, startY);
+
+  let found: Coordinates[] = [];
+  const lookFor = startDigit + 1;
+
+  if (top && Number(top) === lookFor) {
+    found.push(...getRatingOfHead(rows, startX, startY - 1, lookFor));
+  }
+  if (right && Number(right) === lookFor) {
+    found.push(...getRatingOfHead(rows, startX + 1, startY, lookFor));
+  }
+  if (down && Number(down) === lookFor) {
+    found.push(...getRatingOfHead(rows, startX, startY + 1, lookFor));
+  }
+  if (left && Number(left) === lookFor) {
+    found.push(...getRatingOfHead(rows, startX - 1, startY, lookFor));
+  }
+
+  return found;
+}
+
+export function solveSecond(input: string): number {
+  const rows = input.split('\n');
+
+  const trailHeads = findCoordsOfDigit(rows, '0');
+
+  const scores = trailHeads.map(
+    ([startX, startY]) => getRatingOfHead(rows, startX, startY).length
+  );
+
+  return sumArray(scores);
+}