09_2

day09/index.js

@@ -0,0 +1,67 @@
+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 initX = 11, initY = 5;
+const rope = [
+    { x: initX, y: initY },
+    { x: initX, y: initY },
+    { x: initX, y: initY },
+    { x: initX, y: initY },
+    { x: initX, y: initY },
+    { x: initX, y: initY },
+    { x: initX, y: initY },
+    { x: initX, y: initY },
+    { x: initX, y: initY },
+    { x: initX, y: initY }
+];
+
+const visited = new Map();
+
+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++) {
+        rope[0].x += x;
+        rope[0].y += y;
+
+        for(let ropeIndex = 1; ropeIndex < rope.length; ropeIndex++) {
+            if(!isTailAdjacentToHead(rope[ropeIndex - 1], rope[ropeIndex])) {
+                if(rope[ropeIndex - 1].x !== rope[ropeIndex].x && rope[ropeIndex - 1].y !== rope[ropeIndex].y) {
+                    rope[ropeIndex].x += (rope[ropeIndex - 1].x - rope[ropeIndex].x) > 0 ? 1 : -1;
+                    rope[ropeIndex].y += (rope[ropeIndex - 1].y - rope[ropeIndex].y) > 0 ? 1 : -1;
+                } else if(rope[ropeIndex - 1].x === rope[ropeIndex].x) {
+                    rope[ropeIndex].y += (rope[ropeIndex - 1].y - rope[ropeIndex].y) > 0 ? 1 : -1;
+                } else if(rope[ropeIndex - 1].y === rope[ropeIndex].y) {
+                    rope[ropeIndex].x += (rope[ropeIndex - 1].x - rope[ropeIndex].x) > 0 ? 1 : -1;
+                }
+            }            
+        }
+        visited.set(`${rope[rope.length - 1].x}:${rope[rope.length - 1].y}`, true);
+    }   
+});
+
+console.log(visited.size);