day 9, proud of that

2022/9.js

@@ -0,0 +1,81 @@
+const fs = require('fs');
+
+const instructions = fs.readFileSync('9.input').toString().split('\n');
+
+const directions = {
+    U: { x: 0, y: -1 },
+    R: { x: 1, y: 0 },
+    D: { x: 0, y: 1 },
+    L: { x: -1, y: 0 },
+}
+
+const rope = { 
+    segments: [{x: 0, y: 0}, {x: 0, y: 0}],
+    tailHistory: new Set(),
+}
+// add origin
+rope.tailHistory.add(JSON.stringify({ x: 0, y: 0 }));
+
+// we first want a distance vector between the two
+// if it is greater than 2 unit lengths, we want 
+// to move it one closer in the most optimal direction
+const integrateTailSegment = (first, second) => {
+    let dx = first.x - second.x;
+    let dy = first.y - second.y;
+    const distance = Math.round(Math.sqrt(dx * dx + dy * dy));
+    if (distance <= 1) return second;
+    // normalise dx, dy to get a direction vector
+    dx /= distance;
+    dy /= distance;
+    const rx = dx > 0 ? Math.round(dx) : Math.floor(dx);
+    const ry = dy > 0 ? Math.round(dy) : Math.floor(dy);
+    return { x: second.x + rx, y: second.y + ry };
+}
+
+
+// moves by one, up to the caller to itterate
+const processHeadTailMove = (direction) => {
+    rope.segments[0].x += directions[direction].x;
+    rope.segments[0].y += directions[direction].y;
+    rope.segments[1] = integrateTailSegment(rope.segments[0], rope.segments[1]);
+    rope.tailHistory.add(JSON.stringify(rope.segments[1]));
+}
+
+for (const instruction of instructions) {
+    const breakdown = instruction.split(' ');
+    const direction = breakdown[0];
+    const distance = parseInt(breakdown[1]);
+
+    for (let i = 0; i < distance; i++) {
+        processHeadTailMove(direction);
+    }
+}
+
+console.log(`Part 1: ${Array.from(rope.tailHistory).length}`);
+
+const processLongRopeMove = (direction) => {
+    rope.segments[0].x += directions[direction].x;
+    rope.segments[0].y += directions[direction].y;
+
+    for (let i = 1; i < 10; i++)
+        rope.segments[i] = integrateTailSegment(rope.segments[i-1], rope.segments[i]);
+
+    rope.tailHistory.add(JSON.stringify(rope.segments[9]));
+}
+
+rope.segments = [];
+rope.tailHistory = new Set();
+for (let i = 0; i < 10; i++)
+    rope.segments.push({x: 0, y: 0});
+
+for (const instruction of instructions) {
+    const breakdown = instruction.split(' ');
+    const direction = breakdown[0];
+    const distance = parseInt(breakdown[1]);
+
+    for (let i = 0; i < distance; i++) {
+        processLongRopeMove(direction);
+    }
+}
+
+console.log(`Part 2: ${Array.from(rope.tailHistory).length}`);