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0114_flattenBinaryTreeToLinkedList.py
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0114_flattenBinaryTreeToLinkedList.py
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# 0114 - Flatten Binary Tree to Linked List.
'''
Question:
Given the root of a binary tree, flatten the tree into a "linked list":
- The "linked list" should use the same TreeNode class where the right child pointer points
to the next node in the list and the left child pointer is always null.
- The "linked list" should be in the same order as a pre-order traversal of the binary tree.
'''
# Definition for a binary tree node.
class TreeNode(object):
def __init__(self, val=0, left=None, right=None):
self.val = val
self.left = left
self.right = right
class Solution(object):
def __init__(self):
self.prev = None
def flatten(self, root):
"""
:type root: TreeNode
:rtype: None Do not return anything, modify root in-place instead.
"""
if not root:
return None
# Solve the right sub-tree first.
self.flatten(root.right)
self.flatten(root.left)
root.right = self.prev
root.left = None
self.prev = root
if __name__ == '__main__':
pass