Solve round 2 and 3 for 2024

1 files changed, 43 insertions, 0 deletions

diff --git a/2024/puzzle-2.py b/2024/puzzle-2.py
new file mode 100644
index 0000000..98f2efd
--- /dev/null
+++ b/2024/puzzle-2.py
@@ -0,0 +1,43 @@
+lines = []
+with open("2-input", "r") as fp:
+    lines = fp.readlines()
+
+levels = [list(map(int, line.strip().split(" "))) for line in lines]
+
+def is_good_level_1(level):
+    # 1) Is decreasing
+    # 2) Sliding window of two cells (x, y) => 1 <= |x-y| <= 3
+    # figure out if decreasing from first two
+    decreasing = level[0] > level[1]
+    for i in range(len(level) - 1):
+        x = level[i]
+        y = level[i + 1]
+        diff = abs(x - y)
+        if (decreasing and x < y) or (not decreasing and x > y) or not (diff <= 3 and diff >= 1):
+            return False
+    return True
+
+good_levels = [level for level in levels if is_good_level_1(level)]
+print(f"Round 1: {len(good_levels)}")
+
+def check_two_levels(x, y, decreasing):
+    diff = abs(x - y)
+    return not ((decreasing and x < y) or (not decreasing and x > y) or not (diff <= 3 and diff >= 1))
+
+def is_good_level_2(level):
+    # 1) Is decreasing
+    # 2) Sliding window of two cells (x, y) => 1 <= |x-y| <= 3
+    # 3) Can remove any one item to make it safe
+    ret = is_good_level_1(level)
+    if not ret:
+        # Consider slices of the level and check if they're good
+        slices = [level[:i] + level[i + 1:] for i in range(len(level))]
+        for s in slices:
+            if is_good_level_1(s):
+                return True
+    else:
+        return True
+    return False
+
+good_levels = [level for level in levels if is_good_level_2(level)]
+print(f"Round 2: {len(good_levels)}")