From 4be54632379da1c0d35720b199b3fd9fe5e0775e Mon Sep 17 00:00:00 2001
From: Tristan <tristanbeedell@gmail.com>
Date: Sun, 9 Dec 2018 16:20:05 +0000
Subject: [PATCH] 2018 d9 p1 & p2

---
 2018/8/part1.js  |  1 -
 2018/8/test1.txt |  6 ++--
 2018/9/part1.js  | 27 +++++++++++++++
 2018/9/part2.js  | 86 ++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 116 insertions(+), 4 deletions(-)
 create mode 100644 2018/9/part1.js
 create mode 100644 2018/9/part2.js

diff --git a/2018/8/part1.js b/2018/8/part1.js
index 5b58b11..2b8e65f 100644
--- a/2018/8/part1.js
+++ b/2018/8/part1.js
@@ -3,7 +3,6 @@ const input = fs.readFileSync('input.txt', 'utf-8').split('\n')[0].split(' ').ma
 
 function parse(arr) {
 	if (arr[0] == 0) {
-		debugger;
 		return ([2 + arr[1], arr.slice(2, 2 + arr[1])]);
 	}
 	let meta = []
diff --git a/2018/8/test1.txt b/2018/8/test1.txt
index 29b650e..edcb68c 100644
--- a/2018/8/test1.txt
+++ b/2018/8/test1.txt
@@ -1,4 +1,4 @@
 3 2 1 1 0 0 5 0 3 1 2 3 1 0 0 0 67 67
-A - - - - - - - - - - - - - - - 67 67
-    B - - - 5 C - 1 2 3 D - - -
-		    C -                 E -
\ No newline at end of file
+A ----------------------------- 67 67
+    B ------5 C --1-2-3 D------
+		    C--                 E--
\ No newline at end of file
diff --git a/2018/9/part1.js b/2018/9/part1.js
new file mode 100644
index 0000000..bf36fdb
--- /dev/null
+++ b/2018/9/part1.js
@@ -0,0 +1,27 @@
+// input
+let players = 465;
+let last = 71498;
+
+// part 1 : short and extreemly inefficient.
+console.time('speed');
+
+let circle = [0];
+let pointer = 0;
+let elves = [];
+elves.length = players;
+elves.fill(0);
+for (let i = 1; i < last; i++) {
+	if (i % 23 == 0) {
+		let index = pointer - 7 + (pointer - 7 < 0 ? circle.length : 0);
+		elves[i % players] += i + circle[index];
+		circle.splice(index, 1);
+		pointer = index;
+	} else {
+		circle.splice(pointer + 2 - (pointer + 2 > circle.length ? circle.length : 0), 0, i);
+		pointer = circle.indexOf(i);
+	}
+	// console.log(circle.join());
+}
+console.log(Math.max.apply(null, elves));
+
+console.timeEnd('speed');
diff --git a/2018/9/part2.js b/2018/9/part2.js
new file mode 100644
index 0000000..c2b265e
--- /dev/null
+++ b/2018/9/part2.js
@@ -0,0 +1,86 @@
+// input
+let players = 465;
+let last = 7149800;
+
+// part 2 : long but very efficient.
+
+class Marble {
+	constructor(data) {
+		this.data = data;
+		this.next = this;
+		this.prev = this;
+	}
+}
+
+// linked list
+class Circle {
+	constructor() {
+		this.length = 0;
+		this.head = null;
+	}
+
+	add(data, head) {
+		head = head || this.head;
+		const marble = new Marble(data);
+		if (head) {
+			marble.prev = head;
+			marble.next = head.next;
+			marble.prev.next = marble;
+			marble.next.prev = marble;
+		}
+		this.length++;
+		this.head = marble;
+		return marble;
+	}
+
+	remove(marble) {
+		marble = marble || this.head;
+		marble.prev.next = marble.next;
+		marble.next.prev = marble.prev;
+		this.length--;
+		this.head = marble.next;
+		return this.length;
+	}
+
+	moveHead(amt) {
+		for (let i = 0; i < Math.abs(amt); i++) {
+			this.head = amt > 0 ? this.head.next : this.head.prev;
+		}
+		return this.head;
+	}
+
+	print() {
+		let out = `\x1b[32m${this.head.data.toString()}\x1b[0m, `
+		for (let i = 1; i < this.length; i++) {
+			out += `${this.moveHead(1).data.toString()}, `
+		}
+		this.moveHead(1);
+		console.log(out)
+	}
+}
+
+console.time('speed');
+
+circle = new Circle();
+circle.add(0);
+
+// initialise elves with scores of 0
+let elves = [];
+elves.length = players;
+elves.fill(0);
+
+// do all the marbles
+for (let i = 1; i <= last; i++) {
+	if (i % 23 == 0) {
+		circle.moveHead(-7);
+		elves[i % players] += circle.head.data + i;
+		circle.remove();
+	} else {
+		circle.moveHead(1);
+		circle.add(i);
+	}
+	// circle.print();
+}
+console.log(Math.max.apply(null, elves));
+
+console.timeEnd('speed')