Merge other solutions into one file.

day1.cr

@@ -0,0 +1,20 @@
+changes = File.read("day1").split("\n")
+  .select { |it| !it.empty? } 
+  .map(&.to_i)
+
+puts "Final frequency: #{changes.sum}"
+
+count = { 0 => 1 }
+acc = 0
+
+changes.cycle do |i|
+  acc += i
+  old_count = count[acc]? || 0
+  new_count = old_count + 1
+  count[acc] = new_count
+
+  if new_count == 2
+    puts acc
+    exit
+  end
+end

day1_1.cr

@@ -1,4 +0,0 @@
-puts File.read("day1").split("\n")
-  .select { |it| !it.empty? } 
-  .map(&.to_i)
-  .sum

day1_2.cr

@@ -1,19 +0,0 @@
-count = { 0 => 1 }
-acc = 0
-changes = File.read("day1").split("\n")
-  .select { |it| !it.empty? } 
-  .map(&.to_i)
-
-while true
-  changes.each do |i|
-    acc += i
-    old_count = count[acc]? || 0
-    new_count = old_count + 1
-    count[acc] = new_count
-
-    if new_count == 2
-      puts acc
-      exit
-    end
-  end
-end

day2.cr

@@ -0,0 +1,30 @@
+require "./common.cr"
+
+lines = File.read("day2").split("\n")
+lines.pop
+
+CHARS = ('a'..'z').to_a
+
+def has_n?(string, n)
+  return string.chars.count_each(CHARS).any?(&.[](1).==(n))
+end
+
+def count_changes(s1, s2)
+  pairs = s1.chars.zip s2.chars
+  total = 0
+  pairs.each do |pair|
+    total += 1 if pair[0] != pair[1]
+  end
+  return total
+end
+
+two = lines.count { |s| has_n?(s, 2) }
+three = lines.count { |s| has_n?(s, 3) }
+puts "\"Hash\": #{two * three}"
+
+lines.product(lines).each do |pair|
+  if count_changes(pair[0], pair[1]) == 1
+    puts "Strings: #{pair[0]}, #{pair[1]}" 
+    exit
+  end
+end

day2_1.cr

@@ -1,15 +0,0 @@
-lines = File.read("day2").split("\n")
-lines.pop
-
-CHARS = ('a'..'z').to_a
-
-def has_n?(string, n)
-  CHARS.each do |c|
-    return true if string.count(c) == n
-  end
-  return false
-end
-
-two = lines.count { |s| has_n?(s, 2) }
-three = lines.count { |s| has_n?(s, 3) }
-puts two * three

day2_2.cr

@@ -1,15 +0,0 @@
-lines = File.read("day2").split("\n")
-lines.pop
-
-def count_changes(s1, s2)
-  pairs = s1.chars.zip s2.chars
-  total = 0
-  pairs.each do |pair|
-    total += 1 if pair[0] != pair[1]
-  end
-  return total
-end
-
-lines.product(lines).each do |pair|
-  puts "#{pair[0]}, #{pair[1]}" if count_changes(pair[0], pair[1]) == 1
-end