Add the first few solutions.

day4.cr

@@ -0,0 +1,29 @@
+input = File.read("day4.txt").chomp.split("-").map(&.to_i32)
+total = 0
+(input[1] - input[0]).times do |i|
+  invalid = false
+  i = (input[0] + i).to_s
+  i.chars.each_cons_pair do |c1,c2|
+    invalid = c2 < c1
+    break if invalid
+  end
+  next if invalid
+
+  # next unless i =~ /.*(.)\1.*/
+  past_char = nil
+  past_count = 0
+  pasts = [] of Int32
+  i.each_char do |c|
+    if c == past_char
+      past_count += 1
+    else
+      pasts << past_count
+      past_count = 0
+    end
+    past_char = c
+  end
+  pasts << past_count
+
+  total += 1 if pasts.any? &.==(1)
+end
+puts total