AddTwoNumbers_2.java

package com.medium;

/*
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
 */

import org.junit.Test;


/**
 * author : quantin
 * date   : 15/7/18
 */
public class AddTwoNumbers_2 {

	public class ListNode {
		int val;
		ListNode next;
		ListNode(int val) {
			this.val = val;
		}
	}

	public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
		int carry = 0;
		ListNode newHead = new ListNode(0);
		ListNode p1 = l1, p2 = l2, p3 = newHead;


		while (p1 != null || p2 != null) {
			if (p1 != null) {
				carry += p1.val;
				p1 = p1.next;
			}

			if (p2 != null) {
				carry += p2.val;
				p2 = p2.next;
			}

			p3.next = new ListNode(carry % 10);
			p3 = p3.next;
			carry /= 10;
		}

		if (carry == 1)
			p3.next = new ListNode(1);

		return newHead.next;

	}

}