1 files changed, 88 insertions, 0 deletions
diff --git a/2022/20-Grove-Positioning-System/first.js b/2022/20-Grove-Positioning-System/first.js
new file mode 100644
index 0000000..7a49d57
--- /dev/null
+++ b/2022/20-Grove-Positioning-System/first.js
@@ -0,0 +1,88 @@
+import * as fs from "fs";
+
+class File {
+	constructor(line) {
+		this.length = line.length;
+		this.data = line.map(v => ({value: v})); // index in data
+		this.data[0].left = this.data[this.length-1];
+		this.data[0].right = this.data[1];
+		this.data[this.length-1].left = this.data[this.length-2];
+		this.data[this.length-1].right = this.data[0];
+		for (let i=1; i<this.length-1; ++i) {
+			this.data[i].left = this.data[i-1];
+			this.data[i].right = this.data[i+1];
+		}
+		this.data.forEach(v => { if (v.value === 0) this.head = v; });
+	}
+	get(i) {
+		let it = this.head;
+		for (let offset = i % this.length; offset > 0; --offset) {
+			it = it.right;
+		}
+		return it.value;
+	}
+	mix() {
+		this.data.forEach(v => {
+			if (v.value !== 0) {
+				let it = v;
+				let offset; // javascript and modulo... what a nightmare!
+				if (v.value > 0) offset = v.value % (this.length - 1);
+				if (v.value < 0) offset = ((v.value * -1) % (this.length - 1)) * -1;
+				if (offset !==0) {
+					v.right.left = v.left;
+					v.left.right = v.right;
+					if (offset < 0) {
+						for (; offset < 0; ++offset) {
+							it = it.left;
+						}
+						v.right = it;
+						v.left = it.left;
+						v.left.right = v;
+						v.right.left = v;
+					} else {
+						for (; offset > 0; --offset) {
+							it = it.right;
+						}
+						v.right = it.right;
+						v.left = it;
+						v.left.right = v;
+						v.right.left = v;
+					}
+				}
+			}
+		});
+	}
+	print() {
+		let it = this.head;
+		for (let offset = this.length; offset > 0; --offset) {
+			console.log(it.value);
+			it = it.right;
+		}
+		console.log("---");
+	}
+}
+
+function load(filename) {
+	return new File(
+		fs.readFileSync(filename, "utf8")
+		.trim()
+		.split("\n")
+		.map(line => parseInt(line))
+	);
+}
+
+let example = load("example");
+let input = load("input");
+
+function solve(input) {
+	input.mix();
+	return input.get(1000) + input.get(2000) + input.get(3000);
+}
+
+const exampleOutput = solve(example);
+if (exampleOutput !== 3) {
+	console.log("Example failed with " + exampleOutput);
+	process.exit(1); // eslint-disable-line
+}
+
+console.log(solve(input));