099.md

099. Recover Binary Search Tree

Solution 1

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

class Solution(object):
    def recoverTree(self, root):
        """
        :type root: TreeNode
        :rtype: void Do not return anything, modify root in-place instead.
        """
        self.node1, self.node2, self.prev = None, None, None
        self._traversal(root)
        self.node1.val, self.node2.val = self.node2.val, self.node1.val

    def _traversal(self, curr):
        if not curr:
            return
        if curr.left:
            self._traversal(curr.left)
        if self.prev:
            if curr.val < self.prev.val:
                if not self.node1:
                    self.node1 = self.prev
                    self.node2 = curr
                else:
                    self.node2 = curr
        self.prev = curr
        if curr.right:
            self._traversal(curr.right)