12/2024 (part 1)

Author: breadadams

2024/12/index.ts

@@ -0,0 +1,130 @@
+import { getPuzzle } from "../../utils";
+
+const puzzleInput = getPuzzle(__dirname).trim();
+
+const farm = puzzleInput.split("\n").map((row) => row.split(""));
+
+const FARM_HEIGHT = farm.length;
+const FARM_WIDTH = farm[0].length;
+
+type Coordinate = { x: number; y: number };
+
+const directions = {
+  UP: { x: 0, y: -1 },
+  RIGHT: { x: 1, y: 0 },
+  DOWN: { x: 0, y: 1 },
+  LEFT: { x: -1, y: 0 },
+} satisfies Record<string, Coordinate>;
+
+const getCellKey = (cell: Coordinate) => `${cell.x},${cell.y}`;
+
+const getCellFromKey = (key: string) => {
+  const [x, y] = key.split(",").map(Number);
+
+  return { x, y };
+};
+
+const move = (cell: Coordinate, direction: Coordinate) => {
+  return { x: cell.x + direction.x, y: cell.y + direction.y };
+};
+
+const getRegions = () => {
+  const visited = new Set<string>();
+  const regions = new Map<string, { type: string; cells: Set<string> }>();
+
+  for (let y = 0; y < FARM_HEIGHT; y++) {
+    for (let x = 0; x < FARM_WIDTH; x++) {
+      const currentCellKey = getCellKey({ x, y });
+      if (visited.has(currentCellKey)) {
+        continue;
+      }
+
+      const currentCell = farm[y][x];
+
+      regions.set(currentCellKey, {
+        type: currentCell,
+        cells: new Set([currentCellKey]),
+      });
+      const cells = regions.get(currentCellKey).cells;
+
+      const queue = [{ x, y }];
+      const visitedInner = new Set<string>();
+
+      while (queue.length) {
+        const cell = queue.shift();
+        const cellKey = getCellKey(cell);
+
+        if (visitedInner.has(cellKey)) {
+          continue;
+        }
+        visitedInner.add(cellKey);
+
+        for (const direction of Object.values(directions)) {
+          const nextCell = move(cell, direction);
+          const nextCellKey = getCellKey(nextCell);
+
+          if (visitedInner.has(nextCellKey)) {
+            continue;
+          }
+
+          if (
+            nextCell.x < 0 ||
+            nextCell.x >= FARM_WIDTH ||
+            nextCell.y < 0 ||
+            nextCell.y >= FARM_HEIGHT
+          ) {
+            continue;
+          }
+
+          const nextCellValue = farm[nextCell.y][nextCell.x];
+
+          if (nextCellValue === currentCell) {
+            queue.push(nextCell);
+            visited.add(nextCellKey);
+            cells.add(nextCellKey);
+          }
+        }
+      }
+    }
+  }
+
+  return regions;
+};
+
+// Part 1
+(() => {
+  console.time("part 1");
+  const regions = getRegions();
+  let totalPrice = 0;
+
+  for (const [, region] of regions) {
+    const area = region.cells.size;
+    let perimeter = 0;
+
+    for (const regionCellKey of region.cells) {
+      const cell = getCellFromKey(regionCellKey);
+
+      for (const direction of Object.values(directions)) {
+        const neighbourCell = {
+          x: cell.x + direction.x,
+          y: cell.y + direction.y,
+        };
+
+        if (farm?.[neighbourCell.y]?.[neighbourCell.x] !== region.type) {
+          perimeter++;
+        }
+      }
+    }
+
+    totalPrice += area * perimeter;
+  }
+
+  console.log("part 1 totalPrice ::", totalPrice);
+  console.timeEnd("part 1");
+})();
+
+// Part 2
+// (() => {
+//   console.time("part 2");
+//   console.timeEnd("part 2");
+// })();

README.md

@@ -6,6 +6,7 @@
 
 |                    Day                     | Part 1 | Part 2 |
 | :----------------------------------------: | :----: | :----: |
+| [12](https://adventofcode.com/2024/day/12) |   ✅   |   -    |
 | [11](https://adventofcode.com/2024/day/11) |   ✅   |   ✅   |
 | [10](https://adventofcode.com/2024/day/10) |   ✅   |   ✅   |
 | [09](https://adventofcode.com/2024/day/9)  |   ✅   |   ✅   |