Offer.27. Er Cha Shu De Jing Xiang Lcof

剑指 Offer 27.二叉树的镜像 #

Difficulty: 简单

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：

     4  
   /   \  
  2     7  
 / \   / \  
1   3 6   9`

镜像输出：

     4  
   /   \  
  7     2  
 / \   / \  
9   6 3   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 #

DFS #



/**
 * 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) {
            return null;
        }
        TreeNode temp = root.left;
        root.left = mirrorTree(root.right);
        root.right = mirrorTree(temp);
        return root;
    }
}

BFS #

/**
 * 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) {
            return null;
        }
        Stack<TreeNode> stack = new Stack<>();
        stack.add(root);
        while (!stack.isEmpty()) {
            TreeNode node = stack.pop();
            if (node.left != null) {
                stack.add(node.left);
            }
            if (node.right != null) {
                stack.add(node.right);
            }
            TreeNode temp = node.left;
            node.left = node.right;
            node.right = temp;
        }
        return root;
    }
}