Add Two Numbers

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}//构造函数
 * };
 */
class Solution {
public:
    ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
       ListNode dummy(0);//为带头结点的链表
       ListNode* p = &dummy;

        int cn = 0;//表示进位

        while(l1 || l2) {
            int val = cn + (l1 ? l1->val : 0) + (l2 ? l2->val : 0);
            cn = val / 10;
            val = val % 10;//表示当前位
            p->next = new ListNode(val);//申请新结点用来储存val,并利用构造函数初始化
            p = p->next;//形成链表
            if(l1) {
                l1 = l1->next;
            }
            if(l2) {
                l2 = l2->next;
            }
        }

        if(cn != 0) {
            p->next = new ListNode(cn);
            p = p->next;
        }//判断最高位

        return dummy.next;
    }
};

#include<iostream>
using namespace std;

struct ListNode {
    int val;
    ListNode *next;
    ListNode(int x) : val(x), next(NULL) {}//构造函数
};

int main(){
    ListNode list(0),*rear(0),*head(0);
    rear=&list;
    int n;
    while(cin>>n){
        rear->next=new ListNode(n);
        rear=rear->next;
    }//以ctr+z结束 
    head=list.next;
    while(head){
        cout<<head->val<<" ";
        head=head->next;
    }
    return 0;
}