Day 4

2024/04/index.ts

@@ -0,0 +1,41 @@
+const fs = require('fs');
+
+let input = fs.readFileSync(__dirname + '/input.txt', 'utf8');
+
+const vertical: Array<string> = input.split("\n");
+const width = vertical[0].length;
+const height = vertical.length;
+const horizontal: Array<string> = [];
+const diagonalRight: Array<string> = [];
+const diagonalLeft: Array<string> = [];
+
+for (let j = 0; j < height; j++) {
+    for (let i = 0; i < width; i++) {
+        if (!horizontal[i]) {
+            horizontal[i] = '';
+        }
+        horizontal[i] += vertical[j][i];
+        const leftIndex = j+i;
+        if (!diagonalLeft[leftIndex]) {
+            diagonalLeft[leftIndex] = '';
+        }
+        diagonalLeft[leftIndex] += vertical[j][i];
+        const rightIndex = j - i + (Math.max(width, height)) - 1;
+        if (!diagonalRight[rightIndex]) {
+            diagonalRight[rightIndex] = '';
+        }
+        diagonalRight[rightIndex] += vertical[j][i];
+    }
+};
+
+let result = 0;
+
+[vertical, horizontal, diagonalLeft, diagonalRight].forEach((arr) => {
+    arr.forEach((string) => {
+        const fwMatches = string.matchAll(/XMAS/g);
+        const bwMatches = string.matchAll(/SAMX/g);
+        result += Array.from(fwMatches).length + Array.from(bwMatches).length;
+    });
+});
+
+console.log(result);

2024/04/index2.ts

@@ -0,0 +1,28 @@
+const fs = require('fs');
+
+let input = fs.readFileSync(__dirname + '/input.txt', 'utf8');
+
+const vertical: Array<string> = input.split("\n");
+const width = vertical[0].length;
+const height = vertical.length;
+
+let result = 0;
+
+for (let j = 1; j < height - 1; j++) {
+    for (let i = 1; i < width - 1; i++) {
+        const letter = vertical[i][j];
+        if (letter !== 'A') {
+            continue;
+        }
+        const diagonalRight = vertical[i-1][j-1] + 'A' + vertical[i+1][j+1];
+        const diagonalLeft = vertical[i-1][j+1] + 'A' + vertical[i+1][j-1];
+        if (
+            (diagonalLeft === 'MAS' || diagonalLeft === 'SAM')
+            && (diagonalRight === 'MAS' || diagonalRight === 'SAM')
+        ) {
+            result++;
+        }
+    }
+};
+
+console.log(result);