Year 2018 Day 2

2018/day02.rb

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+ids = STDIN.read.split("\n")
+
+def count_for(ids, size)
+  ids.count { |id| id.chars.tally.values.include?(size) }
+end
+
+puts count_for(ids, 2) * count_for(ids, 3)
+
+def part2(ids)
+  ids.combination(2).each do |(a, b)|
+    pairs = a.chars.zip(b.chars)
+    same = pairs.filter { |(x, y)| x == y }
+    return same.map(&:first).join if same.size == pairs.size - 1
+  end
+end
+puts part2(ids)

2018/examples/day02.txt

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+abcde
+fghij
+klmno
+pqrst
+fguij
+axcye
+wvxyz