Add solutions to days 10 and 11

day10.cr

@@ -0,0 +1,37 @@
+require "advent"
+INPUT = input(2020, 10).lines.map(&.to_i32).sort!
+
+def part1(input)
+  diff_1 = 0
+  diff_3 = 0
+  curr = 0
+  input << (input.max + 3)
+  input.each do |i|
+    diff_1 += 1 if (i - curr) == 1
+    diff_3 += 1 if (i - curr) == 3
+    curr = i
+  end
+  puts diff_1 * diff_3
+end
+
+def count_ways(input, prev, index, mem, indent = 0)
+  if m = mem[{prev, index}]?
+    return m 
+  end
+  return 0_i64 if input[index] - prev > 3 || index >= input.size
+  return 1_i64 if index == input.size - 1
+
+  total = count_ways(input, input[index], index+1, mem, indent + 1)
+  total += count_ways(input, prev, index+1, mem, indent + 1)
+
+  mem[{prev, index}] = total
+  return total
+end
+
+def part2(input)
+  input << (input.max + 3)
+  count_ways(input, 0, 0, {} of {Int32, Int32} => Int64)
+end
+
+puts part1(INPUT.clone)
+puts part2(INPUT.clone)