day 9

1 files changed, 22 insertions, 0 deletions

diff --git a/9.py b/9.py
new file mode 100644
index 0000000..a98d67a
--- /dev/null
+++ b/9.py
@@ -0,0 +1,22 @@
+# pyright: strict
+from sys import stdin
+
+
+def predict_next(history: list[int]) -> int:
+    if all(e == 0 for e in history):
+        return 0
+    return history[-1] + predict_next(
+        [a - b for a, b in zip(history[1:], history[:-1])]
+    )
+
+
+def predict_prev(history: list[int]) -> int:
+    if all(e == 0 for e in history):
+        return 0
+    return history[0] - predict_prev([a - b for a, b in zip(history[1:], history[:-1])])
+
+
+histories = [[int(e) for e in l.rstrip().split()] for l in stdin]
+
+print(sum(predict_next(history) for history in histories))
+print(sum(predict_prev(history) for history in histories))