Year 2016 Day 1

2016/day01.rb

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+line = gets.chomp
+
+DIR_CHANGE = {
+  [0, -1] => { 'L' => [-1, 0], 'R' => [1, 0] },
+  [1, 0] => { 'L' => [0, -1], 'R' => [0, 1] },
+  [0, 1] => { 'L' => [1, 0], 'R' => [-1, 0] },
+  [-1, 0] => { 'L' => [0, 1], 'R' => [0, -1] },
+}
+
+pos = [0, 0]
+dir = [0, -1]
+visited = Set.new([pos.to_s])
+p2 = nil
+line.split(', ').each do |s|
+  dir = DIR_CHANGE[dir][s[0]]
+  step_count = s[1..].to_i
+  step_count.times do
+    pos[0] += dir[0]
+    pos[1] += dir[1]
+    p2 = pos.map(&:abs).sum if visited.include?(pos.to_s) && p2.nil?
+    visited.add(pos.to_s)
+  end
+end
+
+puts pos.map(&:abs).sum
+puts p2

2016/examples/day01.txt

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+R8, R4, R4, R8