LeetCode 897 Increasing Order Search Tree 解题报告

题目要求

Given a tree, rearrange the tree in in-order so 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.

题目分析及思路

题目给出一棵树，要求重新对树进行排序，使得树中最左边的结点是树的根，并且每一个结点没有左孩子，只有一个右孩子。可以先得到已知树的中序遍历，再依次创建新的结点并让每一个结点只有一个右孩子。

python代码

# 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') -> 'TreeNode':

def inorder(root):

order = []

if not root:

return order

order.extend(inorder(root.left))

order.append(root.val)

order.extend(inorder(root.right))

return order

in_order = inorder(root)

nodes = []

for v in in_order:

nodes.append(TreeNode(v))

for i, v in enumerate(nodes):

if (i+1) == len(in_order):

break

else:

v.right = nodes[i+1]

return nodes[0]