Day 4 [Part 2]

04/part2.js

@@ -0,0 +1,64 @@
+const { readFileSync } = require("fs");
+// Parse Input
+const inputFile = "input.txt";
+const input = readFileSync(inputFile).toString();
+const grid = [];
+input.split("\n").forEach((line) => grid.push(line.split("")));
+
+const target = "MAS";
+let targetOccurences = [];
+
+const directions = [
+  [-1, -1],
+  [1, -1],
+  [-1, 1],
+  [1, 1],
+];
+
+// Search occurrences
+function search(x, y, dx, dy, currentIndex) {
+  if (currentIndex === target.length) {
+    targetOccurences.push([x - dx, y - dy]);
+    return;
+  }
+
+  const newX = x + dx;
+  const newY = y + dy;
+
+  if (
+    newX >= 0 &&
+    newY >= 0 &&
+    newX < grid[0].length &&
+    newY < grid.length &&
+    grid[newY][newX] === target[currentIndex]
+  ) {
+    search(newX, newY, dx, dy, currentIndex + 1);
+  }
+}
+
+for (let y = 0; y < grid.length; y++) {
+  for (let x = 0; x < grid[0].length; x++) {
+    if (grid[y][x] === target[0]) {
+      for (const [dx, dy] of directions) {
+        search(x, y, dx, dy, 1);
+      }
+    }
+  }
+}
+
+const parsed = [];
+let result = 0;
+
+targetOccurences.forEach((t) => {
+  let found = false;
+  parsed.forEach((p) => {
+    if (p[0] == t[0] && p[1] == t[1] && !found) {
+      result++;
+      found = true;
+    }
+  });
+
+  if (!found) parsed.push(t);
+});
+
+console.log(result);

04/part2.test.js

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+const { readFileSync } = require("fs");
+// Parse Input
+const inputFile = "input.txt";
+const input = readFileSync(inputFile).toString();
+const grid = [];
+input.split("\n").forEach((line) => grid.push(line.split("")));
+
+let result = 0;
+
+for (let y = 1; y < grid.length - 1; y++) {
+  for (let x = 1; x < grid[0].length - 1; x++) {
+    if (grid[y][x] === "A") {
+      if (
+        // Case 1
+        (grid[y - 1][x - 1] === "M" &&
+          grid[y + 1][x + 1] === "S" &&
+          grid[y - 1][x + 1] === "S" &&
+          grid[y + 1][x - 1] === "M") ||
+        // Case 2
+        (grid[y - 1][x - 1] === "S" &&
+          grid[y + 1][x + 1] === "M" &&
+          grid[y - 1][x + 1] === "M" &&
+          grid[y + 1][x - 1] === "S") ||
+        // Case 3
+        (grid[y - 1][x - 1] === "M" &&
+          grid[y + 1][x + 1] === "S" &&
+          grid[y - 1][x + 1] === "M" &&
+          grid[y + 1][x - 1] === "S") ||
+        // Case 4
+        (grid[y - 1][x - 1] === "S" &&
+          grid[y + 1][x + 1] === "M" &&
+          grid[y - 1][x + 1] === "S" &&
+          grid[y + 1][x - 1] === "M") ||
+        // Case 5
+        (grid[y - 1][x - 1] === "M" &&
+          grid[y + 1][x + 1] === "M" &&
+          grid[y - 1][x + 1] === "S" &&
+          grid[y + 1][x - 1] === "S") ||
+        // Case 6
+        (grid[y - 1][x - 1] === "S" &&
+          grid[y + 1][x + 1] === "S" &&
+          grid[y - 1][x + 1] === "M" &&
+          grid[y + 1][x - 1] === "M") ||
+        // Case 7
+        (grid[y - 1][x - 1] === "S" &&
+          grid[y + 1][x + 1] === "M" &&
+          grid[y - 1][x + 1] === "M" &&
+          grid[y + 1][x - 1] === "S") ||
+        // Case 8
+        (grid[y - 1][x - 1] === "M" &&
+          grid[y + 1][x + 1] === "S" &&
+          grid[y - 1][x + 1] === "S" &&
+          grid[y + 1][x - 1] === "M") ||
+        // Case 9
+        (grid[y - 1][x - 1] === "S" &&
+          grid[y + 1][x + 1] === "M" &&
+          grid[y - 1][x + 1] === "M" &&
+          grid[y + 1][x - 1] === "S") ||
+        // Case 10
+        (grid[y - 1][x - 1] === "M" &&
+          grid[y + 1][x + 1] === "S" &&
+          grid[y - 1][x + 1] === "S" &&
+          grid[y + 1][x - 1] === "M")
+      ) {
+        result += 1;
+      }
+    }
+  }
+}
+
+console.log(result);