（链表）从尾到头打印链表

/**
*  struct ListNode {
*        int val;
*        struct ListNode *next;
*        ListNode(int x) :
*              val(x), next(NULL) {
*        }
*  };
*/
class Solution {
public:
    vector<int> printListFromTailToHead(ListNode* head) {
        stack<ListNode*> s;
        ListNode* p = head;
        while(p){
            s.push(p);
            p = p->next;  //将链表从头到尾加入栈中
        }
        vector<int> res;
        while(!s.empty()){
            p = s.top();
            res.push_back(p->val);
            s.pop();
        }
        return res;
    }
};