Add solution for 2015 day 05

2015/README.md

@@ -5,7 +5,7 @@
 - [x] Day 02
 - [x] Day 03
 - [x] Day 04
-- [ ] Day 05
+- [x] Day 05
 - [ ] Day 06
 - [ ] Day 07
 - [ ] Day 08

2015/day-05/inputs/test.txt

@@ -0,0 +1,11 @@
+ugknbfddgicrmopn
+aaa
+jchzalrnumimnmhp
+haegwjzuvuyypxyu
+dvszwmarrgswjxmb
+
+qjhvhtzxzqqjkmpb
+xxyxx
+abccccxix
+uurcxstgmygtbstg
+ieodomkazucvgmuy

2015/day-05/main.rb

@@ -0,0 +1,100 @@
+#!/usr/bin/env -S ruby
+
+require "pathname"
+require "set"
+
+DEBUG = false
+
+INPUTS = [
+  Pathname("inputs/test.txt"),
+  Pathname("inputs/puzzle.txt"),
+].freeze
+VOWELS = %[a e i o u].freeze
+
+def vowel_count(input)
+  input.each_char.sum do |char|
+    VOWELS.include?(char) ? 1 : 0
+  end
+end
+
+def twin_letters(input)
+  input.each_char.each_cons(2).sum do |(char, next_char)|
+    char == next_char ? 1 : 0
+  end
+end
+
+def letter_pairs_count(input)
+  last_index = input.size - 4
+  input
+    .each_char
+    .each_cons(4)
+    .reject { |(a, b, c, d)| (a == b && b == c || b == c && c == d ) && a != d }
+    .each_with_index
+    .flat_map { |(a, b, c, d), i| i == last_index ? [a+b, b+c, c+d] : [a+b] }
+    .tally
+    .values.max || 0
+end
+
+def surrounded_letter_count(input)
+  input
+    .each_char
+    .each_cons(3)
+    .count { |(a, _, b)| a == b }
+end
+
+def is_nice?(input)
+  return false if input.match?(/ab|cd|pq|xy/)
+  return false unless vowel_count(input) >= 3
+  return false unless twin_letters(input) >= 1
+
+  true
+end
+
+def is_really_nice?(input)
+  return false if letter_pairs_count(input) < 2
+  return false if surrounded_letter_count(input).zero?
+
+  true
+end
+
+def count_nice(file)
+  file.each_line.sum do |line|
+    line = line.chomp # chomp: true keyword argument emits warnings
+    next 0 if line.empty?
+    yield(line) ? 1 : 0
+  end
+end
+
+def solve_part_1(file)
+  nice_lines = count_nice(file) do |l|
+    nice = is_nice?(l)
+    if DEBUG
+      puts(nice ? "\t#{l} is nice" : "\t#{l} is not nice")
+      puts "\t" + (" -" * 10)
+    end
+    nice
+  end
+  puts "\tThere are #{nice_lines} nice lines"
+end
+
+def solve_part_2(file)
+  nice_lines = count_nice(file) do |l|
+    nice = is_really_nice?(l)
+    if DEBUG
+      puts(nice ? "\t#{l} is really nice" : "\t#{l} is not really nice")
+      puts "\t" + (" -" * 15)
+    end
+    nice
+  end
+  puts "\tThere are #{nice_lines} really nice lines"
+end
+
+def main(files)
+  files.each do |file|
+    puts "File: #{file}"
+    solve_part_1(file)
+    solve_part_2(file)
+  end
+end
+
+main(INPUTS)