# [leetcode]Recover Binary Search Tree @ Python

Two elements of a binary search tree (BST) are swapped by mistake.

Recover the tree without changing its structure.

# Definition for a  binary tree node
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
# @param root, a tree node
# @return a tree node
def inorder(self, root, list, listp):
if root:
self.inorder(root.left, list, listp)
list.append(root.val); listp.append(root)
self.inorder(root.right, list, listp)
def recoverTree(self, root):
list = []; listp = []
self.inorder(root, list, listp)
list.sort()
for i in range(len(list)):
listp[i].val = list[i]
return root

4

/     \

2        6

/   \    /   \

1    5  3    7

# Definition for a  binary tree node
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
# @param root, a tree node
# @return a tree node
def FindTwoNodes(self, root):
if root:
self.FindTwoNodes(root.left)
if self.prev and self.prev.val > root.val:
self.n2 = root
if self.n1 == None: self.n1 = self.prev
self.prev = root
self.FindTwoNodes(root.right)
def recoverTree(self, root):
self.n1 = self.n2 = None
self.prev = None
self.FindTwoNodes(root)
self.n1.val, self.n2.val = self.n2.val, self.n1.val
return root

posted @ 2014-05-22 22:20  南郭子綦  阅读(3274)  评论(0编辑  收藏  举报