0002 - Add Two Numbers

0002 - Add Two Numbers

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

You may assume the two numbers do not contain any leading zero, except the number 0 itself.

Examples

Input: l1 = [2,4,3], l2 = [5,6,4] Output: [7,0,8] Explanation: 342 + 465 = 807.

Input: l1 = [0], l2 = [0] Output: [0]

Input: l1 = [9,9,9,9,9,9,9], l2 = [9,9,9,9] Output: [8,9,9,9,0,0,0,1]

Constraints

The number of nodes in each linked list is in the range [1, 100]. 0 <= Node.val <= 9 It is guaranteed that the list represents a number that does not have leading zeros.

Java Solution

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode result = new ListNode(0);
        ListNode current = result;
        ListNode p1 = l1;
        ListNode p2 = l2;
        
        int remainder = 0;
        
        while(p1 != null || p2 != null) {
            int firstValue = p1 != null ? p1.val : 0;
            int secondValue = p2 != null ? p2.val : 0;
            
            int sum = firstValue + secondValue + remainder;
            
            remainder = sum / 10;
            current.next = new ListNode(sum % 10);
            current = current.next;
            
            if (p1 != null) p1 = p1.next;
            if (p2 != null) p2 = p2.next;
        }
        if(remainder != 0) current.next = new ListNode(remainder);
        
        return result.next;
    }
}