Leetcode--Add Two Numbers

Problem Description:

You are given two linked lists representing two non-negative numbers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8

分析：按照题意，按照链表数据结构对两个数进行相加，主要是考察链表操作，用两个指针对两个链表进行遍历即可，要注意最后可能有进位，需要增加一个节点的情况，具体代码如下：

/** * 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) {        ListNode *p=l1, *q=l2;        ListNode *head=NULL,*cur=NULL;        if(!p&&!q)            return head;        int flag=0;        while(p&&q)        {            int value=(p->val+q->val+flag)%10;            flag=(p->val+q->val+flag)/10;            ListNode *temp=new ListNode(value);            if(!cur)            {                cur=temp;                head=cur;            }            else            {                cur->next=temp;                cur=temp;            }            p=p->next;            q=q->next;        }        while(p)        {            int value=(p->val+flag)%10;            flag=(p->val+flag)/10;            p->val=value;            cur->next=p;            cur=p;            p=p->next;        }        while(q)        {            int value=(q->val+flag)%10;            flag=(q->val+flag)/10;            q->val=value;            cur->next=q;            cur=q;            q=q->next;        }        if(flag==1)        {            ListNode *temp=new ListNode(1);            cur->next=temp;        }                return head;    }};