Day 12 Part 2

2024/12/index.ts

@@ -14,40 +14,52 @@ const regions: Array<Array<Plot>> = [];
 
 function getAllAdjacentPlots({ x, y }: Coord) {
     const letter = plots[y][x];
-    plots[y][x] = '.'+letter;
+    plots[y][x] = '.' + letter;
 
     const plot = { x, y, edges: 0, corners: 0 };
 
     let adj: Array<Plot> = [plot];
 
-    let firstOneWasAnEdge = false;
-    let lastOneWasAnEdge = false;
+    let adjLetters: Array<string> = [];
+
     [
         { x, y: y - 1 },
+        { x: x + 1, y: y - 1 },
         { x: x + 1, y },
+        { x: x + 1, y: y + 1 },
         { x, y: y + 1 },
+        { x: x - 1, y: y + 1 },
         { x: x - 1, y },
+        { x: x - 1, y: y - 1 },
     ].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++;
+
+        if (i % 2 === 0) {
+            if (adjLetter === letter) {
+                adj = [...adj, ...getAllAdjacentPlots(adjCoord)];
+            } else if (adjLetter !== '.' + letter) {
+                plot.edges++;
             }
-            lastOneWasAnEdge = true;
-        }
-        if (i === 0) {
-            firstOneWasAnEdge = lastOneWasAnEdge;
         }
+        adjLetters.push(adjLetter ? adjLetter.replace('.', '') : '_');
     });
-    if (firstOneWasAnEdge && lastOneWasAnEdge) {
-        plot.corners++;
+
+    for (let i = 1; i < 8; i += 2) {
+        let cornerLetter = adjLetters[i];
+        let beforeLetter = adjLetters[i - 1];
+        let afterLetter = adjLetters[i + 1] || adjLetters[0];
+        if (cornerLetter === letter && (beforeLetter === letter || afterLetter === letter)) {
+            continue;
+        }
+        if (
+            (beforeLetter === letter && afterLetter === letter)
+            || (beforeLetter !== letter && afterLetter !== letter)
+        ) {
+            plot.corners++;
+        }
     }
+
     return adj;
 }
 
@@ -63,7 +75,6 @@ for (let y = 0; y < plots.length; y++) {
     }
 }
 
-console.log(regions);
 let sum = 0;
 
 regions.forEach((plots) => {
@@ -77,4 +88,3 @@ regions.forEach((plots) => {
 });
 
 console.log(sum);
-