Improve solution for day 17.

day-17/solution.py

@@ -1,21 +1,17 @@
 from __future__ import print_function, division
 import fileinput
 from collections import defaultdict
+import bisect
 
-buckets = []
+def value(buckets, choice):
+    total = 0
+    for value in buckets:
+        if choice % 2 == 1:
+            total += value
 
-for line in fileinput.input():
-    buckets.append(int(line))
+        choice //= 2
 
-def works(bucketCombination, target):
-    for idx, value in enumerate(buckets):
-
-        if bucketCombination % 2 == 1:
-            target -= value
-
-        bucketCombination = bucketCombination // 2
-
-    return target == 0
+    return total
 
 def ones(x):
     n = 0
@@ -27,11 +23,40 @@ def ones(x):
 
     return n
 
+def partition(a_list):
+    pivot = len(a_list) // 2
+
+    return a_list[:pivot], a_list[pivot:]
+
+def partitionList(buckets):
+    result = [(value(buckets, x), ones(x)) for x in range(1 << len(buckets))]
+    result.sort()
+    return result
+
+buckets = []
+
+for line in fileinput.input():
+    buckets.append(int(line))
+
+partition1, partition2 = partition(buckets)
+
+values1 = partitionList(partition1)
+values2 = partitionList(partition2)
+
 possible = defaultdict(lambda: 0)
 
-for x in range(1 << len(buckets)):
-    if works(x, 150):
-        n = ones(x)
-        possible[n] += 1
+i = 0
+
+target = 150
+
+for entry in values1:
+
+    i = bisect.bisect_left(values2, (target - entry[0], 0))
+
+    while i < len(values2) and entry[0] + values2[i][0] == target:
+        possible[entry[1] + values2[i][1]] += 1
+        i += 1
+
+print("Total possibilities:", sum(possible.values()))
+print("Minimal possibilities:", possible[min(possible.keys())])
 
-print(sum(possible[x] for x in possible), possible[min(possible.keys())])