Increasing Order Search Tree
Given a binary search tree, rearrange the tree inin-orderso that the leftmost node in the tree is now the root of the tree, and every node has no left child and only 1 right child.
Example 1:
Input:
[5,3,6,2,4,null,8,1,null,null,null,7,9]
5
/ \
3 6
/ \ \
2 4 8
/ / \
1 7 9
Output:
[1,null,2,null,3,null,4,null,5,null,6,null,7,null,8,null,9]
1
\
2
\
3
\
4
\
5
\
6
\
7
\
8
\
9
Note:
The number of nodes in the given tree will be between 1 and 100.
Each node will have a unique integer value from 0 to 1000.
分析
DFS,这里传入尾做参数,空的时候返回
# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution:
def increasingBST(self, root: TreeNode, tail=None) -> TreeNode:
if not root:
return tail
left = self.increasingBST(root.left,root)
root.left = None
root.right = self.increasingBST(root.right,tail)
return left
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