Add Two Numbers · LeetCode

Description

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(javascript)

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} l1
 * @param {ListNode} l2
 * @return {ListNode}
 */
var addTwoNumbers = function(l1, l2) {
    
    let dummyNode = new ListNode(0);
    let newHead = dummyNode;
    let carry = 0;
    
    while(l1 || l2){
        let valueList1 = l1 ? l1.val : 0;
        let valueList2 = l2 ? l2.val : 0;
        
        let sum = valueList1 + valueList2 + carry;
        
        carry = Math.floor(sum/10);
        
        sum = sum % 10;
        
        newHead.next  = new ListNode(sum);
        
        l1 = l1 && l1.next;
        l2 = l2 && l2.next;
        
        newHead = newHead.next;
    }
    
    if(carry > 0) newHead.next = new ListNode(carry);
    
    return dummyNode.next;
}