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 contain a single digit. Add the two numbers and return it as a linked list.

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

Example:

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8
Explanation: 342 + 465 = 807.

Solution


/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode dummy = new ListNode(0);
        ListNode head =  dummy;
        int carry = 0;
        while(l1 != null || l2 != null)
        {
            int val1 = (l1 != null) ? l1.val : 0;
            int val2 = (l2 != null) ? l2.val : 0;
            
            
            int sum = val1 + val2 + carry;
            carry = sum/10;
            
            ListNode newNode = new ListNode(sum%10);
            head.next = newNode;
            head = head.next;
            
            l1 = (l1 != null) ? l1.next : l1;
            l2 = (l2 != null) ? l2.next : l2;
        }
        if(carry != 0)
            head.next = new ListNode(carry);
        
        return dummy.next;
    }
}

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s