From a1cb1a1b16b2304ee2c688e289395c65e4d7a657 Mon Sep 17 00:00:00 2001
From: Piotr Russ <mail@pruss.it>
Date: Sun, 13 Dec 2020 12:27:49 +0100
Subject: day13

---
 day13/data.js    |  5 +++++
 day13/day13-1.js | 10 ++++++++++
 day13/day13-2.js | 22 ++++++++++++++++++++++
 3 files changed, 37 insertions(+)
 create mode 100644 day13/data.js
 create mode 100644 day13/day13-1.js
 create mode 100644 day13/day13-2.js

(limited to 'day13')

diff --git a/day13/data.js b/day13/data.js
new file mode 100644
index 0000000..84e41b5
--- /dev/null
+++ b/day13/data.js
@@ -0,0 +1,5 @@
+const data = `
+1003055
+37,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,41,x,x,x,x,x,x,x,x,x,433,x,x,x,x,x,x,x,23,x,x,x,x,x,x,x,x,17,x,19,x,x,x,x,x,x,x,x,x,29,x,593,x,x,x,x,x,x,x,x,x,x,x,x,13
+`
+module.exports = data
diff --git a/day13/day13-1.js b/day13/day13-1.js
new file mode 100644
index 0000000..16458cd
--- /dev/null
+++ b/day13/day13-1.js
@@ -0,0 +1,10 @@
+const data = require('./data')
+const dataLines = data.split(/\n/g).filter(d => d)
+const currentTime = parseInt(dataLines[0])
+const busses = dataLines[1].split(',').filter(d => d !== 'x').map(d => parseInt(d))
+const timetable = busses
+  .map(b => ({'bus': b, 'time': b - currentTime % b}))
+  .sort((a,b) => a.time - b.time)
+
+console.log('Answer: ', timetable[0].bus * timetable[0].time)
+
diff --git a/day13/day13-2.js b/day13/day13-2.js
new file mode 100644
index 0000000..0e6d11c
--- /dev/null
+++ b/day13/day13-2.js
@@ -0,0 +1,22 @@
+const data = require('./data')
+const [first, ...busses] = data
+  .split('\n')
+  .filter(d => d !== '')[1]
+  .split(',')
+  .map(d => d === 'x' ? null : parseInt(d))
+
+let interval = first, t = 0
+busses.forEach((b, i) => {
+  if (b) {
+    while(true){
+      if ((t+i+1) % b === 0) {
+        interval *= b
+        break
+      }
+      t += interval
+    }
+  }
+})
+
+console.log('Answer: ', t)
+
-- 
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