leetcode二叉树-226翻转二叉树

/**
<p>给你一棵二叉树的根节点 <code>root</code> ，翻转这棵二叉树，并返回其根节点。</p>

<p>&nbsp;</p>

<p><strong>示例 1：</strong></p>

<p><img alt="" src="https://assets.leetcode.com/uploads/2021/03/14/invert1-tree.jpg" style="height: 165px; width: 500px;" /></p>

<pre>
<strong>输入：</strong>root = [4,2,7,1,3,6,9]
<strong>输出：</strong>[4,7,2,9,6,3,1]
</pre>

<p><strong>示例 2：</strong></p>

<p><img alt="" src="https://assets.leetcode.com/uploads/2021/03/14/invert2-tree.jpg" style="width: 500px; height: 120px;" /></p>

<pre>
<strong>输入：</strong>root = [2,1,3]
<strong>输出：</strong>[2,3,1]
</pre>

<p><strong>示例 3：</strong></p>

<pre>
<strong>输入：</strong>root = []
<strong>输出：</strong>[]
</pre>

<p>&nbsp;</p>

<p><strong>提示：</strong></p>

<ul>
	<li>树中节点数目范围在 <code>[0, 100]</code> 内</li>
	<li><code>-100 &lt;= Node.val &lt;= 100</code></li>
</ul>
<div><div>Related Topics</div><div><li>树</li><li>深度优先搜索</li><li>广度优先搜索</li><li>二叉树</li></div></div><br><div><li>👍 1277</li><li>👎 0</li></div>
*/

//leetcode submit region begin(Prohibit modification and deletion)
/**
 * 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 TreeNode invertTree(TreeNode root) {
        if(root == null){
            return null;
        }

        TreeNode temp = root.left;
        root.left = root.right;
        root.right = temp;

        invertTree(root.left);
        invertTree(root.right);
        return root;
    }
}
//leetcode submit region end(Prohibit modification and deletion)