add examples and refactor

Author: shahata

src/2024/day12.js

@@ -1,75 +1,61 @@
-// AAAA
-// BBCD
-// BBCC
-// EEEC
+function countSides(walls) {
+  let sides = 0;
+  walls.forEach(cells => {
+    const points = [...cells].sort((a, b) => a - b);
+    for (let i = 0; i < points.length; i++) {
+      if (points[i] + 1 !== points[i + 1]) sides++;
+    }
+  });
+  return sides;
+}
+
+function walk(map, x, y) {
+  const queue = [{ x, y }];
+  const cells = new Set([`${x},${y}`]);
+  const walls = new Map();
+  let perimeter = 0;
+  while (queue.length > 0) {
+    const p = queue.shift();
+    const neighbors = [
+      { x: p.x - 1, y: p.y },
+      { x: p.x + 1, y: p.y },
+      { x: p.x, y: p.y - 1 },
+      { x: p.x, y: p.y + 1 },
+    ];
+    neighbors.forEach(o => {
+      if (map[o.y]?.[o.x] === map[y][x]) {
+        if (!cells.has(`${o.x},${o.y}`)) {
+          cells.add(`${o.x},${o.y}`);
+          queue.push(o);
+        }
+      } else {
+        perimeter++;
+        if (o.x === p.x) {
+          const wall = `h,${p.y},${o.y}`;
+          walls.set(wall, (walls.get(wall) || new Set()).add(p.x));
+        } else {
+          const wall = `v,${p.x},${o.x}`;
+          walls.set(wall, (walls.get(wall) || new Set()).add(p.y));
+        }
+      }
+    });
+  }
+  return { cells, perimeter, sides: countSides(walls) };
+}
 
 export function part1(input, part2 = false) {
-  let regionId = 0;
   const map = input.split("\n").map(line => line.split(""));
-  const cell2region = new Map();
-  const region2cells = new Map();
-  const region2walls = new Map();
-  const cell2perimeter = new Map();
+  let visited = new Set();
+  let sum = 0;
   for (let y = 0; y < map.length; y++) {
     for (let x = 0; x < map[y].length; x++) {
-      if (cell2region.has(`${x},${y}`)) continue;
-      const walls = new Map();
-      regionId++;
-      region2walls.set(regionId, walls);
-      region2cells.set(regionId, new Set());
-      let currentRegion = map[y][x];
-      const queue = [{ x, y }];
-      while (queue.length > 0) {
-        const p = queue.shift();
-        cell2region.set(`${p.x},${p.y}`, regionId);
-        region2cells.get(regionId).add(`${p.x},${p.y}`);
-        const neighbors = [
-          { x: p.x - 1, y: p.y },
-          { x: p.x + 1, y: p.y },
-          { x: p.x, y: p.y - 1 },
-          { x: p.x, y: p.y + 1 },
-        ];
-        neighbors.forEach(o => {
-          if (map[o.y]?.[o.x] === currentRegion) {
-            if (!cell2region.has(`${o.x},${o.y}`)) {
-              cell2region.set(`${o.x},${o.y}`, regionId);
-              queue.push(o);
-            }
-          } else {
-            const perimeter = cell2perimeter.get(`${p.x},${p.y}`) || 0;
-            cell2perimeter.set(`${p.x},${p.y}`, perimeter + 1);
-
-            if (o.x === p.x) {
-              let wall = `horizontal,${p.y},${o.y}`;
-              if (!walls.has(wall)) walls.set(wall, new Set());
-              walls.get(wall).add(p.x);
-            } else {
-              let wall = `vertical,${p.x},${o.x}`;
-              if (!walls.has(wall)) walls.set(wall, new Set());
-              walls.get(wall).add(p.y);
-            }
-          }
-        });
-      }
+      if (visited.has(`${x},${y}`)) continue;
+      const { cells, perimeter, sides } = walk(map, x, y);
+      visited = visited.union(cells);
+      if (!part2) sum += cells.size * perimeter;
+      else sum += cells.size * sides;
     }
   }
-  let sum = 0;
-  for (const regionId of region2cells.keys()) {
-    const cells = region2cells.get(regionId);
-    const area = cells.size;
-    let perimeter = 0;
-    cells.forEach(cell => (perimeter += cell2perimeter.get(cell) || 0));
-    const walls = region2walls.get(regionId);
-    let sides = 0;
-    walls.forEach(cells => {
-      const points = [...cells].sort((a, b) => a - b);
-      for (let i = 0; i < points.length; i++) {
-        if (points[i] + 1 !== points[i + 1]) sides++;
-      }
-    });
-    if (!part2) sum += area * perimeter;
-    else sum += area * sides;
-  }
   return sum;
 }
 

src/2024/day12.spec.js

@@ -7,6 +7,27 @@ describe("day12 2024", () => {
   describe("part1", () => {
     test("it should work for part 1 examples", () => {
       expect(part1(["AAAA", "BBCD", "BBCC", "EEEC"].join("\n"))).toEqual(140);
+
+      expect(
+        part1(["OOOOO", "OXOXO", "OOOOO", "OXOXO", "OOOOO"].join("\n")),
+      ).toEqual(772);
+
+      expect(
+        part1(
+          [
+            "RRRRIICCFF",
+            "RRRRIICCCF",
+            "VVRRRCCFFF",
+            "VVRCCCJFFF",
+            "VVVVCJJCFE",
+            "VVIVCCJJEE",
+            "VVIIICJJEE",
+            "MIIIIIJJEE",
+            "MIIISIJEEE",
+            "MMMISSJEEE",
+          ].join("\n"),
+        ),
+      ).toEqual(1930);
     });
 
     test("it should work for part 1 input", () => {
@@ -17,6 +38,39 @@ describe("day12 2024", () => {
   describe("part2", () => {
     test("it should work for part 2 examples", () => {
       expect(part2(["AAAA", "BBCD", "BBCC", "EEEC"].join("\n"))).toEqual(80);
+
+      expect(
+        part2(["OOOOO", "OXOXO", "OOOOO", "OXOXO", "OOOOO"].join("\n")),
+      ).toEqual(436);
+
+      expect(
+        part2(["EEEEE", "EXXXX", "EEEEE", "EXXXX", "EEEEE"].join("\n")),
+      ).toEqual(236);
+
+      expect(
+        part2(
+          ["AAAAAA", "AAABBA", "AAABBA", "ABBAAA", "ABBAAA", "AAAAAA"].join(
+            "\n",
+          ),
+        ),
+      ).toEqual(368);
+
+      expect(
+        part2(
+          [
+            "RRRRIICCFF",
+            "RRRRIICCCF",
+            "VVRRRCCFFF",
+            "VVRCCCJFFF",
+            "VVVVCJJCFE",
+            "VVIVCCJJEE",
+            "VVIIICJJEE",
+            "MIIIIIJJEE",
+            "MIIISIJEEE",
+            "MMMISSJEEE",
+          ].join("\n"),
+        ),
+      ).toEqual(1206);
     });
 
     test("it should work for part 2 input", () => {