226.Invert Binary Tree

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 {    /*     * 递归遍历整个树的每一个节点     * 并且若该节点不为空，则让其左右子节点互换     */    public TreeNode invertTree(TreeNode root) {                if(root == null)            return root;                    TreeNode transit = root.left;        root.left = root.right;        root.right = transit;                if(root.left != null)            root.left = invertTree(root.left);        if(root.right != null)            root.right = invertTree(root.right);        return root;    }}