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BinaryTreeInorderTraversal.py
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BinaryTreeInorderTraversal.py
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from typing import List
# Definition for a binary tree node.
class TreeNode:
def __init__(self, x):
self.val = x
self.left = None
self.right = None
# Recursive
class Solution1:
def inorderTraversal(self, root: TreeNode) -> List[int]:
if root is None:
return []
result = []
result += self.inorderTraversal(root.left)
result.append(root.val)
result += self.inorderTraversal(root.right)
return result
# iteration
class Solution2:
def inorderTraversal(self, root: TreeNode) -> List[int]:
stack, result = [], []
while True:
while root:
stack.append(root)
root = root.left
if not stack:
return result
node = stack.pop()
result.append(node.val)
root = node.right
########
# Test #
########
# 1
# / \
# 2 3
# / \
# 4 5
# /
# 6
root = TreeNode(1)
node1 = TreeNode(2)
node2 = TreeNode(3)
node3 = TreeNode(4)
node4 = TreeNode(5)
node5 = TreeNode(6)
root.left = node1
root.right = node2
node1.left = node3
node1.right = node4
node4.left = node5
result = Solution2().inorderTraversal(root)
print(result)
# expected: [4, 2, 6, 5, 1, 3]