1 files changed, 45 insertions, 0 deletions
diff --git a/20/main.py b/20/main.py
new file mode 100755
index 0000000..c20cc5c
--- /dev/null
+++ b/20/main.py
@@ -0,0 +1,45 @@
+#!/usr/bin/python
+
+from math import sqrt
+
+
+
+def solve_partn(partn, target):
+    house = 1
+    while True:
+        # Find all divisors of the house number, because those
+        # determine which elves brings presents to which house.
+        # If I were smart, I'd cache the results and use them in
+        # both parts 1 and 2, but I can't be bothered to do that.
+        divs = [1, house]
+        for n in range(2, int(sqrt(house)) + 1):
+            if house % n == 0:
+                divs += [n, house / n]
+
+        # Give gifts to each house as described in the puzzle text
+        gifts = 0
+        for d in divs:
+            if partn == 1:
+                gifts += 10 * d
+            else: # partn == 2
+                if house / d <= 50:
+                    gifts += 11 * d
+
+        if gifts >= target:
+            return house
+
+        house += 1
+
+
+
+def main():
+    # My personalized puzzle input
+    target = 34000000
+
+    print("Part 1 solution:", solve_partn(1, target)) # 786240 for me
+    print("Part 2 solution:", solve_partn(2, target)) # 831600 for me
+
+
+
+if __name__ == "__main__":
+    main()