1 files changed, 35 insertions, 0 deletions
diff --git a/day9/day9.py b/day9/day9.py
new file mode 100644
index 0000000..3bd8155
--- /dev/null
+++ b/day9/day9.py
@@ -0,0 +1,35 @@
+"""Day 9."""
+from itertools import permutations
+
+with open("input") as f:
+    nums = [int(x) for x in f.read().rstrip().split("\n")]
+
+preamble_length = 25
+invalid_number = None
+
+# Part 1
+for idx, val in enumerate(nums[preamble_length:], start=preamble_length):
+    pre = nums[idx - preamble_length: idx]
+    valid = False
+    for combs in permutations(pre, 2):
+        if sum(combs) == val:
+            valid = True
+    if not valid:
+        invalid_number = val
+        print(invalid_number)
+        break
+
+# Part 2
+found = False
+for x in range(len(nums)):
+    for y in range(x + 1, len(nums)):
+        subset = nums[x:y]
+        total = sum(subset)
+        if total > invalid_number:
+            break
+        if total == invalid_number:
+            print(min(subset) + max(subset))
+            found = True
+            break
+    if found:
+        break