LeetCode-Add Two Numbers-链表数字相加-链表操作+加法进位

https://oj.leetcode.com/problems/add-two-numbers/

跟大整数类似的链表操作。注意最后还有进位时需要再加入一个结点。

/**
 * 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) {
        if (l1==NULL) return l2;
        int up=0;
        ListNode *p=l1;
        ListNode *q=l2;
        ListNode *t=NULL;
        ListNode *h=NULL;
        while(p || q){
            int vp=0,vq=0;
            if (p!=NULL){
                vp=p->val;
                p=p->next;
            }
            else{vp=0;}
            if (q!=NULL){
                vq=q->val;
                q=q->next;
            }
            else{vq=0;}
            int cur=vp+vq+up;
            up=cur/10;
            cur=cur%10;
            ListNode *cp= new ListNode(cur);
            if (t!=NULL) {
                t->next=cp;
                t=cp;
            }
            else{
                t=cp;
                h=cp;
            }
        }
        if (up) {
            t->next=new ListNode(up);
        }
        return h;
    }
};