Invert a binary tree.
4 / \ 2 7 / \ / \1 3 6 9
to
4 / \ 7 2 / \ / \9 6 3 1
/** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */public class Solution { public TreeNode invertTree(TreeNode root) { if(root!=null) { TreeNode tmp = root.left; root.left = root.right; root.right = tmp; invertTree(root.left); invertTree(root.right); } return root; }}