Solve 2024-12

Add side-aware coordinate utils

2024/12/index.ts

@@ -0,0 +1,113 @@
+import { sumArray } from '../../utils/array.ts';
+import {
+  calculateSides,
+  type Coordinates,
+  getAdjacent,
+  getNeighbouringSides,
+  isCoordinateEqual
+} from '../../utils/coordinates.ts';
+
+function searchNeighbours(
+  visited: Set<number>,
+  rows: string[],
+  char: string,
+  x: number,
+  y: number,
+  found: Coordinates
+) {
+  const position = y * rows.length + x;
+  if (visited.has(position)) {
+    return;
+  }
+  visited.add(position);
+  found.push([x, y]);
+
+  const { left, top, right, down } = getAdjacent(rows, x, y);
+  if (left === char) {
+    searchNeighbours(visited, rows, char, x - 1, y, found);
+  }
+  if (top === char) {
+    searchNeighbours(visited, rows, char, x, y - 1, found);
+  }
+  if (right === char) {
+    searchNeighbours(visited, rows, char, x + 1, y, found);
+  }
+  if (down === char) {
+    searchNeighbours(visited, rows, char, x, y + 1, found);
+  }
+}
+
+function groupChars(input: string) {
+  const rows = input.split('\n');
+
+  const groups: { char: string; coords: Coordinates }[] = [];
+  const visited = new Set<number>();
+
+  for (let y = 0; y < rows.length; y++) {
+    for (let x = 0; x < rows[y].length; x++) {
+      const position = y * rows.length + x;
+      if (visited.has(position)) {
+        continue;
+      }
+      const char = rows[y][x];
+      const coords: Coordinates = [];
+      searchNeighbours(visited, rows, char, x, y, coords);
+
+      groups.push({ char, coords });
+    }
+  }
+  return groups;
+}
+
+function getPerimeter(g: Coordinates): number {
+  if (g.length === 1) {
+    return 4;
+  }
+  if (g.length === 2) {
+    return 6;
+  }
+  const { uniqueSides } = calculateSides(g);
+
+  return uniqueSides.length;
+}
+
+export function solveFirst(input: string): number {
+  const groups = groupChars(input);
+
+  return sumArray(groups.map((g) => g.coords.length * getPerimeter(g.coords)));
+}
+
+export function solveSecond(input: string): number {
+  const groups = groupChars(input);
+
+  return sumArray(groups.map((g) => g.coords.length * getSides(g.coords)));
+}
+
+export function getSides(g: Coordinates): number {
+  if (g.length === 1) {
+    return 4;
+  }
+  if (g.length === 2) {
+    return 4;
+  }
+  const { uniqueSides } = calculateSides(g);
+
+  const visited = new Set<number>();
+
+  let sides = 0;
+  for (let i = 0; i < uniqueSides.length; i++) {
+    if (visited.has(i)) {
+      continue;
+    }
+    visited.add(i);
+    sides++;
+
+    const { neighbours } = getNeighbouringSides(uniqueSides[i], uniqueSides);
+
+    neighbours.forEach((c) =>
+      visited.add(uniqueSides.findIndex((v) => isCoordinateEqual(v, c)))
+    );
+  }
+
+  return sides;
+}