剑指 Offer 27. 二叉树的镜像

题目

请完成一个函数,输入一个二叉树,该函数输出它的镜像。

例如输入:

graph TB
4((4)) --- 2((2))
4 --- 7((7))
2 --- 1((1))
2 --- 3((3))
7 --- 6((6))
7 --- 9((9))

镜像输出:

graph TB
4((4)) --- 7((7))
4 --- 2((2))
7 --- 9((9))
7 --- 6((6))
2 --- 3((3))
2 --- 1((1))

示例 1:
输入:root = [4,2,7,1,3,6,9]
输出:[4,7,2,9,6,3,1]

限制:
0 <= 节点个数 <= 1000

注意:本题与主站226题相同

题解

public TreeNode mirrorTree(TreeNode root) {
    if (root == null) {
        return null;
    }

    TreeNode mirror = new TreeNode(root.val);
    mirror.right = this.mirrorTree(root.left);
    mirror.left = this.mirrorTree(root.right);

    return mirror;
}