From 492bdb29fd0eb2cbb661e197f164ba1a8045c24c Mon Sep 17 00:00:00 2001
From: TimStallard <code@timstallard.me.uk>
Date: Sun, 10 Dec 2017 12:18:49 +0000
Subject: [PATCH] day 10

---
 day10/part1.js | 18 ++++++++++++++++++
 day10/part2.js | 27 +++++++++++++++++++++++++++
 2 files changed, 45 insertions(+)
 create mode 100644 day10/part1.js
 create mode 100644 day10/part2.js

diff --git a/day10/part1.js b/day10/part1.js
new file mode 100644
index 0000000..79c0a3d
--- /dev/null
+++ b/day10/part1.js
@@ -0,0 +1,18 @@
+var list = [];
+for(var i = 0; i < 256; i++){
+	list.push(i);
+}
+var pos = 0;
+var lengths = [97,167,54,178,2,11,209,174,119,248,254,0,255,1,64,190];
+var skip = 0;
+for(var length of lengths){
+	for(var i = 0; i < (length/2); i++){
+		var a = list[(pos+i)%list.length];
+		var b = list[(pos+length-1-i)%list.length];
+		list[(pos+i)%list.length] = b;
+		list[(pos+length-1-i)%list.length] = a;
+	}
+	pos += length + skip;
+	skip += 1;
+}
+console.log(list[0] * list[1]);
diff --git a/day10/part2.js b/day10/part2.js
new file mode 100644
index 0000000..98af73a
--- /dev/null
+++ b/day10/part2.js
@@ -0,0 +1,27 @@
+function hash(input){
+	var list = [];
+	for(var i = 0; i < 256; i++){
+		list.push(i);
+	}
+	var pos = 0;
+	var lengths = input.split("").filter((a)=>(a)).map((a)=>(a.charCodeAt(0))).concat([17, 31, 73, 47, 23]);
+	var skip = 0;
+	for(var x = 0; x < 64; x++){
+		for(var length of lengths){
+			for(var i = 0; i < (length/2); i++){
+				var a = list[(pos+i)%list.length];
+				var b = list[(pos+length-1-i)%list.length];
+				list[(pos+i)%list.length] = b;
+				list[(pos+length-1-i)%list.length] = a;
+			}
+			pos += length + skip;
+			pos = pos % list.length;
+			skip += 1;
+		}
+	}
+
+	var hash = list.reduce((arr, a, i)=>{arr[Math.floor(i/16)] = arr[Math.floor(i/16)] ^ a; return arr;}, []);
+	return hash.map((a)=>(a.toString(16))).map((a)=>((a.length == 1) ? ("0" + a) : (a))).join("");
+}
+
+console.log(hash("97,167,54,178,2,11,209,174,119,248,254,0,255,1,64,190"));