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  • [leetcode]Flatten Binary Tree to Linked List @ Python

    原题地址:http://oj.leetcode.com/problems/flatten-binary-tree-to-linked-list/

    题意:

    Given a binary tree, flatten it to a linked list in-place.

    For example,
    Given

             1
            / 
           2   5
          /    
         3   4   6
    

    The flattened tree should look like:

       1
        
         2
          
           3
            
             4
              
               5
                
                 6
    Hints:

    If you notice carefully in the flattened tree, each node's right child points to the next node of a pre-order traversal.

    由上面可以看出:这道题的意思是将一颗二叉树平化(flatten)为一条链表,而链表的顺序为二叉树的先序遍历。

    解题思路:首先将左右子树分别平化为链表,这两条链表的顺序分别为左子树的先序遍历和右子树的先序遍历。然后将左子树链表插入到根节点和右子树链表之间,就可以了。左右子树的平化则使用递归实现。

    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:
        # @param root, a tree node
        # @return nothing, do it in place
        def flatten(self, root):
            if root == None:
                return
            self.flatten(root.left)
            self.flatten(root.right)
            p = root
            if p.left == None:
                return
            p = p.left
            while p.right:
                p = p.right
            p.right = root.right
            root.right = root.left
            root.left = None
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  • 原文地址:https://www.cnblogs.com/zuoyuan/p/3721157.html
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