002-Add-Two-Numbers.js

/**
 * https://leetcode.com/problems/add-two-numbers/description/
 * Difficulty: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 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.
 */

// Definition for singly-linked list.
function ListNode(val) {
    this.val = val;
    this.next = null;
}

/**
 * @param {ListNode} l1
 * @param {ListNode} l2
 * @return {ListNode}
 */
var addTwoNumbers = function (l1, l2) {

    var c = 0;
    var ret = new ListNode(0);
    var curr = ret;

    while (l1 || l2) {
        var a = l1 ? l1.val : 0;
        var b = l2 ? l2.val : 0;
        var sum = a + b + c;
        c = Math.floor(sum / 10);
        curr.next = new ListNode(sum % 10);
        if (l1) {
            l1 = l1.next;
        }
        if (l2) {
            l2 = l2.next;
        }
        curr = curr.next;
    }
    if (c) {
        curr.next = new ListNode(c);
    }

    return ret.next;
};