二叉树-面试题27-二叉树的镜像

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public TreeNode mirrorTree(TreeNode root) {
        if(root==null){ //递归边界，当越过叶节点时递归结束
            return null;
        }
        TreeNode temp=root.left;  //暂存root的左子节点
        root.left=mirrorTree(root.right);  //进入递归 修改节点
        root.right=mirrorTree(temp);
        return root;
    }
}