Time: 241 ms (90.60%), Space: 52.4 MB (37.25%) - LeetHub

Author: hogan-tech

2096-step-by-step-directions-from-a-binary-tree-node-to-another/2096-step-by-step-directions-from-a-binary-tree-node-to-another.py

@@ -0,0 +1,71 @@
+# time complexity: O(n)
+# space complexity: O(n)
+from typing import List
+
+
+class TreeNode:
+    def __init__(self, val=0, left=None, right=None):
+        self.val = val
+        self.left = left
+        self.right = right
+
+
+class Solution:
+    def getDirections(
+        self, root: TreeNode, startValue: int, destValue: int
+    ) -> str:
+        lowestCommonAncestor = self.findLCA(root, startValue, destValue)
+        pathToStart = []
+        pathToDest = []
+        self.findPath(lowestCommonAncestor, startValue, pathToStart)
+        self.findPath(lowestCommonAncestor, destValue, pathToDest)
+        directions = []
+        directions.extend("U" * len(pathToStart))
+        directions.extend(pathToDest)
+
+        return "".join(directions)
+
+    def findLCA(
+        self, node: TreeNode, value1: int, value2: int
+    ) -> TreeNode:
+        if node is None:
+            return None
+        if node.val == value1 or node.val == value2:
+            return node
+        leftLCA = self.findLCA(node.left, value1, value2)
+        rightLCA = self.findLCA(node.right, value1, value2)
+        if leftLCA is None:
+            return rightLCA
+        elif rightLCA is None:
+            return leftLCA
+        else:
+            return node
+
+    def findPath(
+        self, node: TreeNode, targetValue: int, path: List[str]
+    ) -> bool:
+        if node is None:
+            return False
+        if node.val == targetValue:
+            return True
+        path.append("L")
+        if self.findPath(node.left, targetValue, path):
+            return True
+        path.pop()
+        path.append("R")
+        if self.findPath(node.right, targetValue, path):
+            return True
+        path.pop()
+        return False
+
+
+startValue = 3
+destValue = 6
+root = TreeNode(5)
+root.left = TreeNode(1)
+root.left.left = TreeNode(3)
+root.right = TreeNode(2)
+root.right.left = TreeNode(6)
+root.right.right = TreeNode(4)
+
+print(Solution().getDirections(root, startValue, destValue))