给你一棵二叉树的根节点 root ,翻转这棵二叉树,并返回其根节点。
示例 1:
输入:root = [4,2,7,1,3,6,9]
输出:[4,7,2,9,6,3,1]
示例 2:
输入:root = [2,1,3]
输出:[2,3,1]
示例 3:
输入:root = []
输出:[]
提示:
树中节点数目范围在 [0, 100] 内
-100 <= Node.val <= 100
来源:力扣(LeetCode)
链接:https://leetcode.cn/problems/invert-binary-tree
思路:
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode() {}
* TreeNode(int val) { this.val = val; }
* TreeNode(int val, TreeNode left, TreeNode right) {
* this.val = val;
* this.left = left;
* this.right = right;
* }
* }
*/
class Solution {
public TreeNode invertTree(TreeNode root) {
//dayinroot
if(root == null){
return null ;
}
TreeNode result = new TreeNode(root.val);
qianxu(root,result);
return result;
}
//前序遍历
public void qianxu(TreeNode root,TreeNode result) {
if(root.left != null){
result.right = new TreeNode(root.left.val);
qianxu(root.left,result.right);
}
if(root.right != null){
result.left = new TreeNode(root.right.val);
qianxu(root.right,result.left);
}
}
}