package LeetCode;

public class LeetCode226 {

    /// 226. Invert Binary Tree
    /// https://leetcode.com/problems/invert-binary-tree/description/
    /// 时间复杂度: O(n), n为树中节点个数
    /// 空间复杂度: O(h), h为树的高度

    public class TreeNode {
        int val;
        TreeNode left;
        TreeNode right;

        TreeNode(int x) {
            val = x;
        }
    }

    public TreeNode invertTree(TreeNode root) {

        if (root == null)
            return null;

        // 左边翻转，右边翻转
        TreeNode left = invertTree(root.left);
        TreeNode right = invertTree(root.right);

        // 左右交换！
        root.left = right;
        root.right = left;

        return root;
    }
}