## DEV Community

MD ARIFUL HAQUE

Posted on • Updated on

Medium

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:

``````/**
* Definition for a singly-linked list.
* class ListNode {
*     public \$val = 0;
*     public \$next = null;
*     function __construct(\$val = 0, \$next = null) {
*         \$this->val = \$val;
*         \$this->next = \$next;
*     }
* }
*/
class Solution {

/**
* @param ListNode \$l1
* @param ListNode \$l2
* @return ListNode
*/
\$p = \$l1;
\$q = \$l2;
\$carry = 0;

while (\$p !== null || \$q !== null) {
\$x = (\$p !== null) ? \$p->val : 0;
\$y = (\$q !== null) ? \$q->val : 0;
\$sum = \$carry + \$x + \$y;
\$carry = (int)(\$sum / 10);

\$curr->next = new ListNode(\$sum % 10);
\$curr = \$curr->next;

if (\$p !== null) {
\$p = \$p->next;
}
if (\$q !== null) {
\$q = \$q->next;
}
}

if (\$carry > 0) {
\$curr->next = new ListNode(\$carry);
}