114 lines
2.7 KiB
Java
114 lines
2.7 KiB
Java
//给你一个二叉树的根节点 root ，请你将此二叉树上下翻转，并返回新的根节点。
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//
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// 你可以按下面的步骤翻转一棵二叉树：
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//
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//
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// 原来的左子节点变成新的根节点
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// 原来的根节点变成新的右子节点
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// 原来的右子节点变成新的左子节点
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//
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//
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// 上面的步骤逐层进行。题目数据保证每个右节点都有一个同级节点（即共享同一父节点的左节点）且不存在子节点。
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//
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//
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//
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// 示例 1：
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//
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//
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//输入：root = [1,2,3,4,5]
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//输出：[4,5,2,null,null,3,1]
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//
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//
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// 示例 2：
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//
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//
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//输入：root = []
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//输出：[]
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//
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//
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// 示例 3：
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//
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//
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//输入：root = [1]
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//输出：[1]
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//
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//
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//
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//
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// 提示：
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//
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//
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// 树中节点数目在范围 [0, 10] 内
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// 1 <= Node.val <= 10
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// 树中的每个右节点都有一个同级节点（即共享同一父节点的左节点）
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// 树中的每个右节点都没有子节点
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//
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// Related Topics 树 深度优先搜索 二叉树 👍 102 👎 0
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package leetcode.editor.cn;
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import com.code.leet.entiy.TreeNode;
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//156:上下翻转二叉树
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public class BinaryTreeUpsideDown {
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public static void main(String[] args) {
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Solution solution = new BinaryTreeUpsideDown().new Solution();
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// TO TEST
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TreeNode n1 = new TreeNode(1);
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TreeNode n2 = new TreeNode(2);
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TreeNode n3 = new TreeNode(3);
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TreeNode n4 = new TreeNode(4);
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TreeNode n5 = new TreeNode(5);
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n1.left = n2;
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n1.right = n3;
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n2.left = n4;
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n2.right = n5;
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solution.upsideDownBinaryTree(n1);
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}
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//leetcode submit region begin(Prohibit modification and deletion)
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/**
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* Definition for a binary tree node.
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* public class TreeNode {
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* int val;
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* TreeNode left;
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* TreeNode right;
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* TreeNode() {}
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* TreeNode(int val) { this.val = val; }
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* TreeNode(int val, TreeNode left, TreeNode right) {
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* this.val = val;
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* this.left = left;
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* this.right = right;
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* }
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* }
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*/
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class Solution {
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public TreeNode upsideDownBinaryTree(TreeNode root) {
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if (root == null || root.left == null) {
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return root;
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}
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dfs(root);
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root.left = null;
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root.right = null;
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return node;
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}
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TreeNode node;
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TreeNode temp;
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private void dfs(TreeNode root) {
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if (root == null || root.left == null) {
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node = root;
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temp = root;
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return;
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}
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dfs(root.left);
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temp.left = root.right;
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temp.right = root;
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temp = root;
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}
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}
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//leetcode submit region end(Prohibit modification and deletion)
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}
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