Solution for Day 10

day_10/first.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+input = File.readlines('./input').map(&:to_i).sort
+
+$d = { 1 => 0, 2 => 0, 3 => 0 }
+$j = 0
+input << input.max + 3
+
+input.each do |adapter|
+  diff = adapter - $j
+  if diff.between? 1, 3
+    $d[diff] += 1
+    $j = adapter
+  end
+end
+
+puts $d[1] * $d[3]

day_10/input

@@ -0,0 +1,104 @@
+165
+78
+151
+15
+138
+97
+152
+64
+4
+111
+7
+90
+91
+156
+73
+113
+93
+135
+100
+70
+119
+54
+80
+170
+139
+33
+123
+92
+86
+57
+39
+173
+22
+106
+166
+142
+53
+96
+158
+63
+51
+81
+46
+36
+126
+59
+98
+2
+16
+141
+120
+35
+140
+99
+121
+122
+58
+1
+60
+47
+10
+87
+103
+42
+132
+17
+75
+12
+29
+112
+3
+145
+131
+18
+153
+74
+161
+174
+68
+34
+21
+24
+85
+164
+52
+69
+65
+45
+109
+148
+11
+23
+129
+84
+167
+27
+28
+116
+110
+79
+48
+32
+157
+130

day_10/second.rb

@@ -0,0 +1,12 @@
+# frozen_string_literal: true
+
+input = File.readlines('./input').map(&:to_i).sort
+
+input << input.max + 3
+
+$c = { 0 => 1 }
+
+input.each do |e|
+  $c[e] = $c.values_at(e - 1, e - 2, e - 3).compact.sum
+end
+puts $c[input.last]