226.翻转二叉树

力扣题目链接(opens new window)

翻转一棵二叉树。

/**
 * 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 void swap(TreeNode root){
        TreeNode tempNode;
        tempNode  = root.left;
        root.left = root.right;
        root.right = tempNode;
    }
    public TreeNode invertTree(TreeNode root) {//中序遍历交换左右子树
        if(root == null) return root;
        swap(root);//根
        invertTree(root.left);//左
        invertTree(root.right);//右
        return root;
    }
}