操作给定的二叉树，将其变换为源二叉树的镜像。

class Solution {
public:
         //栈的非递归
     void Mirror(TreeNode *pRoot) {
         if (pRoot == NULL)return;
         stack<TreeNode*> st;
         TreeNode* p = NULL;
         st.push(pRoot);
         while (st.size())
         {
             p = st.top();
             st.pop();
             swap(p->left, p->right);
             if (p->left)st.push(p->left);
             if (p->right)st.push(p->right);
         }
     }  //队列的非递归
    void Mirror(TreeNode *pRoot) {
         if (pRoot == NULL)return;
         queue<TreeNode*> qu;
         TreeNode* p = NULL;
         qu.push(pRoot);
         while (qu.size())
         {
             p = qu.front();
             qu.pop();
             swap(p->left, p->right);
             if (p->left)qu.push(p->left);
             if (p->right)qu.push(p->right);
         }
    }
    //递归
    void Mirror(TreeNode *pRoot) {
         if (pRoot == NULL)return;
         swap(pRoot->left, pRoot->right);
         Mirror(pRoot->left);
         Mirror(pRoot->right);
    }
};