Day 12 partial

2024/12/index.ts

@@ -0,0 +1,80 @@
+const fs = require('fs');
+
+const input = fs.readFileSync(__dirname + '/input.txt', 'utf8');
+
+interface Coord { x: number, y: number };
+interface Plot { x: number, y: number, edges: number, corners: number };
+
+const plots: Array<Array<string>> = input.split("\n").slice(0, -1).map((row: string) => row.split(''));
+
+const height = plots.length;
+const width = plots[0].length;
+
+const regions: Array<Array<Plot>> = [];
+
+function getAllAdjacentPlots({ x, y }: Coord) {
+    const letter = plots[y][x];
+    plots[y][x] = '.'+letter;
+
+    const plot = { x, y, edges: 0, corners: 0 };
+
+    let adj: Array<Plot> = [plot];
+
+    let firstOneWasAnEdge = false;
+    let lastOneWasAnEdge = false;
+    [
+        { x, y: y - 1 },
+        { x: x + 1, y },
+        { x, y: y + 1 },
+        { x: x - 1, y },
+    ].forEach((adjCoord, i) => {
+        const adjLetter = plots[adjCoord.y]
+            && plots[adjCoord.y][adjCoord.x]
+            && plots[adjCoord.y][adjCoord.x];
+        if (adjLetter === letter) {
+            adj = [...adj, ...getAllAdjacentPlots(adjCoord)];
+            lastOneWasAnEdge = false;
+        } else if (adjLetter !== '.'+letter) {
+            plot.edges++;
+            if (lastOneWasAnEdge) {
+                plot.corners++;
+            }
+            lastOneWasAnEdge = true;
+        }
+        if (i === 0) {
+            firstOneWasAnEdge = lastOneWasAnEdge;
+        }
+    });
+    if (firstOneWasAnEdge && lastOneWasAnEdge) {
+        plot.corners++;
+    }
+    return adj;
+}
+
+for (let y = 0; y < plots.length; y++) {
+    const row = plots[y];
+    for (let x = 0; x < row.length; x++) {
+        const char = row[x];
+        if (char.startsWith('.')) {
+            continue;
+        }
+
+        regions.push(getAllAdjacentPlots({ x, y }));
+    }
+}
+
+console.log(regions);
+let sum = 0;
+
+regions.forEach((plots) => {
+    const perim = plots.reduce((carry, { edges }) => carry + edges, 0);
+    const vertices = plots.reduce((carry, { corners }) => carry + corners, 0);
+    const area = plots.length;
+    // Part 1
+    // sum += perim * area;
+    // Part 2
+    sum += vertices * area;
+});
+
+console.log(sum);
+