feat: 1372. Longest ZigZag Path in a Binary Tree

src/binary_tree/dfs/longest_zigzag_path_in_a_binary_tree/solution.py

@@ -0,0 +1,22 @@
+from typing import Optional
+from structures import TreeNode
+
+
+class Solution:
+    def dfs(
+        self, root: Optional[TreeNode], prev_direction: str, cur_length: int
+    ) -> int:
+        if root is None:
+            return cur_length - 1
+        if prev_direction == "left":
+            right_length = self.dfs(root.right, "right", cur_length + 1)
+            left_length = self.dfs(root.left, "left", 1)
+        else:
+            right_length = self.dfs(root.right, "right", 1)
+            left_length = self.dfs(root.left, "left", cur_length + 1)
+        return max(left_length, right_length)
+
+    def longestZigZag(self, root: Optional[TreeNode]) -> int:
+        right_length = self.dfs(root.right, "right", 1)
+        left_length = self.dfs(root.left, "left", 1)
+        return max(right_length, left_length)

tests/test_longest_zigzag_path_in_a_binary_tree.py

@@ -0,0 +1,17 @@
+import pytest
+from src.binary_tree.dfs.longest_zigzag_path_in_a_binary_tree.solution import Solution
+from test_utils import TreeBuilder
+
+
+@pytest.mark.parametrize(
+    "root, expected",
+    [
+        ([1, None, 2, 3, 4, None, None, 5, 6, None, 7, None, None, None, 8], 3),
+        ([1, 1, 1, None, 1, None, None, 1, 1, None, 1], 4),
+        ([1], 0),
+    ],
+)
+def test_max_depth(root, expected):
+    root = TreeBuilder.from_list(root)
+    solution = Solution()
+    assert solution.longestZigZag(root) == expected