Description：
Invert a binary tree.
4
/ \
2 7
/ \ / \
1 3 6 9
to
4
/ \
7 2
/ \ / \
9 6 3 1
递归invert就好了。
/**
* 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)
return null;
invert(root);
return root; }
public static void invert(TreeNode root) {
if(root==null || (root.right == null && root.left==null)) {
return;
}
TreeNode rNode = root.right;
TreeNode lNode = root.left;
root.right = lNode;
root.left = rNode;
invert(root.left);
invert(root.right);
}
}