leetcode 445. Add Two Numbers II

用栈先存着两个node的东西，再pop出来相加。

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/** * Definition for singly-linked list. * struct ListNode { *     int val; *     ListNode *next; *     ListNode(int x) : val(x), next(NULL) {} * }; */class Solution {public:    ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {        int cf = 0;        stack<int> q_1;        stack<int> q_2;        while(l1 != NULL || l2 != NULL)        {            if(l1 != NULL)            {                q_1.push(l1->val);                l1 = l1->next;            }                if(l2 != NULL)                {                q_2.push(l2->val);                l2 = l2->next;            }            }        ListNode *rel = NULL;        while(!q_1.empty() && !q_2.empty())        {            int a1 = q_1.top(), a2 = q_2.top();            cout << a1 << "  " << a2 << endl;            int sum_tmp = q_1.top() + q_2.top() + cf;            q_1.pop();            q_2.pop();            cf = sum_tmp/10;            sum_tmp = sum_tmp%10;            ListNode *tmp = new ListNode(sum_tmp);            tmp->next = rel;            rel = tmp;        }        while(!q_1.empty())        {            int tmp_q_1 = q_1.top() + cf;            q_1.pop();            cf = tmp_q_1/10;            tmp_q_1 = tmp_q_1 % 10;            ListNode *tmp2 = new ListNode(tmp_q_1);            tmp2->next = rel;            rel = tmp2;                    }        while(!q_2.empty())        {            int tmp3 = q_2.top() + cf;            q_2.pop();            cf = tmp3/10;            tmp3 = tmp3 % 10;            ListNode *tmp2 = new ListNode(tmp3);            tmp2->next = rel;            rel = tmp2;                     }        if(cf)        {            ListNode *tmp = new ListNode(cf);            tmp->next = rel;            rel = tmp;        }        /*        while(rel != NULL)        {            cout << rel->val << endl;            rel = rel->next;        }*/        return rel;    }};