Implement memoization

day12/src/day12.moon

@@ -48,7 +48,26 @@ isPotentialSolution = (pattern, lengths) ->
  return false
  #reverseLengths == 0
 
+memoized = {}
+hit = 0
+miss = 0
+
 solveImpl = (pattern, lengths, i) ->
+ memoize = false
+ local memoizationKey
+
+ if (#pattern - i + 1) < 5
+ memoizationKey = table.concat {string.sub(pattern, i), table.concat(lengths, ',')}, ';'
+ if memoized[memoizationKey]
+ hit += 1
+ return memoized[memoizationKey]
+ miss += 1
+ memoize = true
+ if (hit + miss) % 1000000 == 0
+ print "Hit rate: #{hit / (hit + miss)}"
+ hit = 0
+ miss = 0
+
  if #lengths == 0
  if i > #pattern or prefixLength(pattern, i, '[^#]') == #pattern - i + 1
  return 1
@@ -82,6 +101,9 @@ solveImpl = (pattern, lengths, i) ->
  -- The group matches, conceptually place a . thereafter and continue...
  solutions += solveImpl pattern, remLengths, nextI + 1
 
+ if memoize
+ memoized[memoizationKey] = solutions
+
  solutions
 
 solve = (pattern, lengths) ->
@@ -105,7 +127,7 @@ for {pattern, lengths} in *input
 
  longPattern = "#{pattern}?#{pattern}?#{pattern}?#{pattern}?#{pattern}"
  longLengths = [length for i = 1, 5 for length in *lengths]
- part2 += solve longPattern, longLengths
+ -- part2 += solve longPattern, longLengths
 
  i += 1