Invert a binary tree.
4
/ \
2 7
/ \ / \
1 3 6 9
to
4
/ \
7 2
/ \ / \
9 6 3 1
Trivia:
This problem was inspired by this original tweet by Max Howell:
解题思路：
递归即可，JAVA实现如下：
public TreeNode invertTree(TreeNode root) {
if(root==null)
return root;
TreeNode temp=root.left;
root.left=root.right;
root.right=temp;
invertTree(root.left);
invertTree(root.right);
return root;
}