/**
 * struct TreeNode {
 *	int val;
 *	struct TreeNode *left;
 *	struct TreeNode *right;
 *	TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 * };
 */
class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定,请勿修改,直接返回方法规定的值即可
     *
     * 
     * @param pRoot TreeNode类 
     * @return TreeNode类
     */
    TreeNode* temp=nullptr;

    TreeNode* Mirror(TreeNode* pRoot) {
        // write code here
        if(!pRoot)
            return pRoot;

        // 左右子树交换
        temp = pRoot->left;
        pRoot->left = pRoot->right;
        pRoot->right = temp;    

        // 递归左右子树
        Mirror(pRoot->left);
        Mirror(pRoot->right);

        return pRoot;
    }
};