09_1

day09/index.js

@@ -0,0 +1,52 @@
+import { readFileSync } from "fs";
+
+const input = readFileSync("movements.txt", "utf-8");
+
+function isTailAdjacentToHead(head, tail) {
+    if(Math.abs(tail.x - head.x) > 1) return false;
+    if(Math.abs(tail.y - head.y) > 1) return false;
+    return true;
+}
+
+const head = { x: 0, y: 0}, tail = { x: 0, y: 0 };
+
+const visited = new Map([[ `0:0`, true ]]);
+
+input.split('\n').forEach(line => {
+    const operations = line.split(' ');
+
+    let x = 0, y = 0;
+
+    switch(operations[0]) {
+        case "U":
+            y++;
+            break;
+        case "D":
+            y--;
+            break;
+        case "L":
+            x--;
+            break;
+        case "R":
+            x++;
+            break;
+    }
+
+    for(let i = 0; i < parseInt(operations[1]); i++) {
+        const oldHead = {};
+        oldHead.x = head.x;
+        oldHead.y = head.y;
+
+        head.x += x;
+        head.y += y;
+
+        if(!isTailAdjacentToHead(head, tail)) {
+            tail.x = oldHead.x;
+            tail.y = oldHead.y;
+
+            visited.set(`${tail.x}:${tail.y}`, true);
+        }
+    }
+});
+
+console.log(visited.size);