Java Program for Add Two Numbers Solution - LeetCode

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.

Example 1:

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

Example 2 :

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

Example 3 :

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.

Solution :

class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
       ListNode sentinel = new ListNode(0);
        ListNode curr = sentinel;
        int carry = 0;

        while (l1 != null || l2 != null) {
            int x = l1 != null ? l1.val : 0;
            int y = l2 != null ? l2.val : 0;

            int sum = carry + x + y;

            carry = sum / 10;

            curr.next = new ListNode(sum % 10);
            curr = curr.next;   
            if(l1 != null) l1 = l1.next;
            if(l2 != null) l2=l2.next;
        }
        if (carry > 0) {
        curr.next = new ListNode(carry);
    }
        return sentinel.next;
    }
}