From 5a28775f19a8a48b67fc41e048c2a3958afa1e42 Mon Sep 17 00:00:00 2001
From: Marcin Chrzanowski <marcin.j.chrzanowski@gmail.com>
Date: Fri, 25 Dec 2020 15:26:01 +0100
Subject: Add day 10

---
 10/a.rb      |  10 ++++++
 10/b.rb      |   7 ++++
 10/input.txt | 102 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 119 insertions(+)
 create mode 100644 10/a.rb
 create mode 100644 10/b.rb
 create mode 100644 10/input.txt

diff --git a/10/a.rb b/10/a.rb
new file mode 100644
index 0000000..34336ef
--- /dev/null
+++ b/10/a.rb
@@ -0,0 +1,10 @@
+lines = File.readlines('input.txt').map { |l| l.to_i }
+lines.sort!
+lines.unshift(0)
+lines.push(lines.last + 3)
+diffs = Hash.new 0
+lines.each_cons 2 do |chargers|
+  diffs[chargers[1]  - chargers[0]] += 1
+end
+
+puts diffs[1] * diffs[3]
diff --git a/10/b.rb b/10/b.rb
new file mode 100644
index 0000000..d27f1ab
--- /dev/null
+++ b/10/b.rb
@@ -0,0 +1,7 @@
+lines = File.readlines('input.txt').map { |l| l.to_i }.unshift(0).sort!
+arrs = Hash.new 0
+arrs[0] = 1
+lines.slice(1, lines.size).each do |line|
+  arrs[line] += arrs[line - 1] + arrs[line - 2] + arrs[line - 3]
+end
+puts arrs[lines.last]
diff --git a/10/input.txt b/10/input.txt
new file mode 100644
index 0000000..5b0d755
--- /dev/null
+++ b/10/input.txt
@@ -0,0 +1,102 @@
+153
+17
+45
+57
+16
+147
+39
+121
+75
+70
+85
+134
+128
+115
+51
+139
+44
+65
+119
+168
+122
+72
+105
+31
+103
+89
+154
+114
+55
+25
+48
+38
+132
+157
+84
+71
+113
+143
+83
+64
+109
+129
+120
+100
+151
+79
+125
+22
+161
+167
+19
+26
+118
+142
+4
+158
+11
+35
+56
+18
+40
+7
+150
+99
+54
+152
+60
+27
+164
+78
+47
+82
+63
+46
+91
+32
+135
+3
+108
+10
+159
+127
+69
+110
+126
+133
+28
+15
+104
+138
+160
+98
+90
+144
+1
+2
+92
+41
+86
+66
+95
+12
-- 
cgit v1.2.3