19_二叉树的镜像

class TreeNode {
int val;
TreeNode left;
TreeNode right;
}

public class Solution{
public void Mirror(TreeNode root){
if(root == null)
return;
if(root.left == null && root.right == null)
return;

//如果遍历到的有子节点就交换两个子节点
TreeNode temp = root.left;
root.left = root.right;
root.right = temp;

//先序遍历每个节点
if(root.left != null)
Mirror(root.left);
if(root.right != null)
Mirror(root.right);
}

public static void main(String[] args){

}
}