【剑指offer】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<int> s;    //利用栈“先进后出”的性质
        while(head != NULL)
        {
            s.push(head->val);
            head = head->next;
        }
        vector<int> ans;
        while(!s.empty())
        {
            ans.push_back(s.top());
            s.pop();
        }
        return ans;
    }
};