19、二叉树的镜像

越来越喜欢递归了！

/**
public class TreeNode {
int val = 0;
TreeNode left = null;
TreeNode right = null;

public TreeNode(int val) {
this.val = val;

}

}
*/
public class Solution {
public void Mirror(TreeNode root) {
if(root == null) return;
//if(root.left == null && root.right == null) return;
if(root.left != null) Mirror(root.left);
if(root.right != null) Mirror(root.right);
TreeNode temp = root.left;
root.left = root.right;
root.right = temp;
}
}