将一个二叉树左右翻转(Java 版)

public class Solution 
{
  public TreeNode invertTree(TreeNode root) 
  {
    if (root == null) 
    {
      return null;
    }
    root.left = invertTree(root.left);
    root.right = invertTree(root.right);

    TreeNode tmp = root.left;
    root.left = root.right;
    root.right = tmp;
    return root;
  }
}