Add Two Numbers

一、题目要求

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

二、代码实现

  ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
             if(l1==NULL && l2==NULL)
			return NULL;
		else if(l1==NULL)
			return l2;
		else if(l2==NULL)
			return l1;
		//
		//stack<int> num;
		queue<int> num1,num2,num;
		ListNode* head,*start,*next;
		head=l1;
		while(head!=NULL)
		{
			num1.push(head->val);
			head=head->next;
		}
		head=l2;
		while(head!=NULL)
		{
			num2.push(head->val);
			head=head->next;
		}
		//
		int flag=0,result;
		while(!num1.empty()||!num2.empty())
		{
			if(!num1.empty()&&!num2.empty())
			{
				result=num1.front()+num2.front()+flag;
				if(result>=10)
					flag=1;
				else
					flag=0;
				result=result%10;
				num.push(result);
				num1.pop();
				num2.pop();
			}
			else if(!num1.empty())
			{
				result=num1.front()+flag;
				if(result>=10)
					flag=1;
				else
					flag=0;
				result=result%10;
				num.push(result);
				num1.pop();
			}
			else
			{
				result=num2.front()+flag;
				if(result>=10)
					flag=1;
				else
					flag=0;
				result=result%10;
				num.push(result);
				num2.pop();
			}
		}
		if(flag)
			num.push(flag);
		//
		start=new ListNode(num.front());
		num.pop();
		head=start;
		while(!num.empty())
		{
			next=new ListNode(num.front());
			num.pop();
			start->next=next;
			start=start->next;
		}

		return head;
    }