Solutions to day 13.

day-13/solution.py

@@ -0,0 +1,50 @@
+import fileinput
+import re
+from itertools import permutations
+
+linePattern = re.compile(r"(\w+) would (gain|lose) (\d+) happiness units by sitting next to (\w+)\.")
+
+ratings = {}
+
+
+# Read the input by regex
+for line in fileinput.input():
+    match = linePattern.match(line)
+    person = match.group(1)
+    if person not in ratings:
+        ratings[person] = {}
+
+    value = int(match.group(3))
+    if match.group(2) == "lose":
+        value *= -1
+
+    target = match.group(4)
+    ratings[person][target] = value
+
+maxHappiness = 0
+maxWithMe = 0
+
+# Compute happiness with everyone present
+for permutation in permutations(ratings.keys()):
+    happiness = 0
+    withMe = 0
+
+    for i in range(len(permutation)):
+        target = permutation[i]
+        neighbour1 = permutation[(i + 1) % len(permutation)]
+        neighbour2 = permutation[(i - 1 + len(permutation)) % len(permutation)]
+
+        happiness += ratings[target][neighbour1]
+        if i < len(permutation) - 1:
+            withMe += ratings[target][neighbour1]
+
+        happiness += ratings[target][neighbour2]
+        if i > 0:
+            withMe += ratings[target][neighbour2]
+
+    maxHappiness = max(maxHappiness, happiness)
+    maxWithMe = max(maxWithMe, withMe)
+
+
+print maxHappiness, maxWithMe
+