Day 12 [Part 2]

12/part2.js

@@ -0,0 +1,128 @@
+const { readFileSync } = require("fs");
+// Parse Input
+const inputFile = "input.txt";
+const input = readFileSync(inputFile).toString();
+const grid = [];
+input
+  .trim()
+  .split("\n")
+  .forEach((line) => grid.push(line.split("")));
+
+const directions = [
+  [0, -1],
+  [0, 1],
+  [-1, 0],
+  [1, 0],
+];
+
+function isInGrid(coord) {
+  let x = coord[0];
+  let y = coord[1];
+  return !(x < 0 || y < 0 || x >= grid[0].length || y >= grid.length);
+}
+
+let areas = [];
+let parsed = [];
+
+for (let y = 0; y < grid.length; y++) {
+  const line = grid[y];
+  for (let x = 0; x < line.length; x++) {
+    if (!parsed.find((c) => c[0] == x && c[1] == y)) {
+      let currentValue = grid[y][x];
+      let currentArea = {
+        id: areas.length,
+        value: currentValue,
+        corners: 0,
+        items: [],
+      };
+      let toParse = [[x, y]];
+      let internalToCheck = [];
+      while (toParse.length > 0) {
+        let e = toParse.pop();
+        if (parsed.find((c) => c[0] == e[0] && c[1] == e[1]) != null) continue;
+        parsed.push(e);
+
+        currentArea.items.push(e);
+
+        let currentFences = [];
+        directions.forEach((d, i) => {
+          let nd = [d[0] + e[0], d[1] + e[1]];
+          if (isInGrid(nd) && grid[nd[1]][nd[0]] == currentArea.value) {
+            toParse.push(nd);
+          } else {
+            currentFences.push([nd, i]);
+          }
+        });
+
+        if (currentFences.length == 4) {
+          currentArea.corners = currentArea.corners + 4;
+        } else {
+          internalToCheck.push(e);
+          if (
+            currentFences.length == 3 ||
+            (currentFences.length == 2 &&
+              !(
+                (currentFences[0][1] == 0 && currentFences[1][1] == 1) ||
+                (currentFences[0][1] == 2 && currentFences[1][1] == 3)
+              ))
+          ) {
+            currentArea.corners =
+              currentArea.corners + currentFences.length - 1;
+          }
+        }
+      }
+
+      // Check Internal Corners
+      internalToCheck.forEach((e) => {
+        currentArea.corners =
+          currentArea.corners + checkInternalCorners(e, currentArea);
+      });
+      currentArea.items = currentArea.items.length;
+      areas.push(currentArea);
+    }
+  }
+}
+
+function hasCoordInList(coord, list) {
+  return list.some(([x, y]) => x === coord[0] && y === coord[1]);
+}
+
+function checkInternalCorners(coord, area) {
+  const crossDirections = [
+    [0, -1],
+    [1, -1],
+    [1, 0],
+    [1, 1],
+    [0, 1],
+    [-1, 1],
+    [-1, 0],
+    [-1, -1],
+    [0, -1],
+  ];
+
+  let patern = [];
+  let result = 0;
+
+  crossDirections.forEach((d, i) => {
+    let nd = [d[0] + coord[0], d[1] + coord[1]];
+    patern.push(hasCoordInList(nd, area.items));
+
+    if (patern.length == 3) {
+      if (
+        patern[0] == true &&
+        patern[1] == false &&
+        patern[2] == true &&
+        [0, 2, 4, 6, 8].includes(i)
+      )
+        result += 1;
+      patern.shift();
+    }
+  });
+
+  return result;
+}
+
+let result = 0;
+
+areas.forEach((a) => (result += a.corners * a.items));
+console.log(result);