leetcode刷题之树(4)-递归:翻转树 leetcode

[LeetCode] Invert Binary Tree 翻转二叉树
Invert a binary tree.

4 /\ 27 / \/ \ 13 69

4 /\ 72 / \/ \ 96 31

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 fuck off.

两种递归的解法：
第一种递归函数返回翻转完后的根节点

class Solution { public TreeNode invertTree(TreeNode root) { if(root == null) return null; TreeNode left = root.left; // 后面的操作会改变 left 指针，因此先保存下来 root.left = invertTree(root.right); root.right = invertTree(left); return root; } }

第二种：递归函数没有返回值前序遍历调换左右节点这个容易理解

class Solution { public TreeNode invertTree(TreeNode root) { invert(root); return root; } private void invert(TreeNode root){ if(root == null) return; TreeNode node = root.left; root.left = root.right; root.right = node; invert(root.left); invert(root.right); } }

【leetcode刷题之树(4)-递归:翻转树】