[LeetCode] 226. Invert Binary Tree
阿新 • • 發佈:2018-12-17
#題目 Invert a binary tree.
Example:
Input:
4
/ 2 7 / \ / 1 3 6 9 Output:
4
/ 7 2 / \ / 9 6 3 1 Trivia: This problem was inspired by this original tweet by Max Howell:
Google: 90% of our engineers use the software you wrote (Homebrew), but you can’t invert a binary tree on a whiteboard so f*** off.
思路
遞迴,遞迴函式將傳輸節點的 左右子樹互換。
code
# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
def inverNode(node):
if node == None:
return None
tmp = inverNode(node.right)
node.right = inverNode(node.left)
node.left = tmp
return node
class Solution:
def invertTree(self, root):
"""
:type root: TreeNode
:rtype: TreeNode
"""
return inverNode(root)
遞迴函式 的輸入是 結點,返回 已經將其左右子結點 交換的 結點。
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
class Solution {
public TreeNode invertTree(TreeNode root) {
if(root == null) return null;
TreeNode cleft = root.left;
root.left = invertTree(root.right);
root.right = invertTree(cleft);
return root;
}
}