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

AddTwoNumbers.cpp

// AddTwoNumbers.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"

/**
* Definition for singly-linked list.
* struct ListNode {
*     int val;
*     ListNode *next;
*     ListNode(int x) : val(x), next(NULL) {}
* };
*/

struct ListNode {
	int val;
	ListNode *next;
	ListNode(int x) : val(x), next(NULL) {}
};

class Solution 
{
public:
	ListNode *addTwoNumbers(ListNode *l1, ListNode *l2) 
	{
		// IMPORTANT: Please reset any member data you declared, as
		// the same Solution instance will be reused for each test case.
		if (l1 == NULL)
			return l2;
		if (l2 == NULL)
			return l1;

		ListNode *head = NULL;
		ListNode *p1 = l1;
		ListNode *p2 = l2;
		ListNode *p, *q;
		int carry = 0;

		while (p1 != NULL && p2 != NULL)
		{
			int sum = p1->val + p2->val + carry;
			carry = sum / 10;
			sum = sum % 10;

			p = new ListNode(sum);
			if (head == NULL)
			{
				head = p;
				q = p;
			}
			else
			{
				q->next = p;
				q = p;
			}
			
			p1 = p1->next;
			p2 = p2->next;
		}

		while (p1 != NULL)
		{
			int sum = p1->val + carry;
			carry = sum / 10;
			sum = sum % 10;

			p = new ListNode(sum);
			if (head == NULL)
			{
				head = p;
				q = p;
			}
			else
			{
				q->next = p;
				q = p;
			}
			
			p1 = p1->next;
		}
		
		while (p2 != NULL)
		{
			int sum = p2->val + carry;
			carry = sum / 10;
			sum = sum % 10;

			p = new ListNode(sum);
			if (head == NULL)
			{
				head = p;
				q = p;
			}
			else
			{
				q->next = p;
				q = p;
			}
			p2 = p2->next;
		}

		if (carry == 1)
		{
			p = new ListNode(carry);
			q->next = p;
		}

		return head;
	}

	ListNode *createList(int input[], int length)
	{
		ListNode *head = NULL;
		ListNode *p, *q;

		for (int i = 0; i < length; i++)
		{
			p = new ListNode(input[i]);
			if (i == 0)
			{
				head = p;
				q = p;
			}
			else
			{
				q->next = p;
				q = p;
			}
		}

		return head;
	}
};

int _tmain(int argc, _TCHAR* argv[])
{
	Solution s;

	int inputArray1[] = { 0 };
	int inputArray2[] = { 0 };
	ListNode *input1 = s.createList(inputArray1, 1);
	ListNode *input2 = s.createList(inputArray2, 1);
	ListNode *result = s.addTwoNumbers(input1, input2);
	
	return 0;
}