题解 | #判断一个链表是否为回文结构#

//增加一个栈用来存储需要反向的层 class Solution { public: vector<vector > Print(TreeNode* pRoot) {

    queue<TreeNode*>q;
    stack<TreeNode*>stc;
    q.push(pRoot);
    vector<vector<int>>result;
    if(pRoot == nullptr){
        return result;
    }
    bool flag = false;
    while(!q.empty()){
        int floor_size = q.size();
        flag = !flag;
        vector<int>mid;
        for(int i = 0; i < floor_size; ++i){
            TreeNode *temp = q.front();
            q.pop();
            if(flag){//不用反向
                mid.push_back(temp->val);
            }else{
                stc.push(temp);
            }
            if(temp->left){
                q.push(temp->left);
            }
            if(temp->right){
                q.push(temp->right);
            }
        }
        while(!stc.empty()){
            TreeNode* t = stc.top();
            stc.pop();
            mid.push_back(t->val);
        }
        result.push_back(mid);      
    }
    return result;
}

};