LeetCode - 23 - Merge k Sorted Lists

 /**

 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode[]} lists
 * @return {ListNode}
 */
var mergeKLists = function(lists) {
    var n = lists.length;
    if (n == 0) {
        return null;
    }
    if (n == 1) {
        return lists[0];
    }
    var newLists = [];
    for (var i = 0; i < n - 1 ; i += 2) {
        newLists.push(mergeTwoLists(lists[i], lists[i+1]));
    }
    if (lists.length % 2 == 1) {
        newLists.push(lists[n-1]);
    }
    return mergeKLists(newLists);
};

function mergeTwoLists(list1, list2) {
    var mergedList = new ListNode(null, null);
    var pointer1 = list1, pointer2 = list2, pointer3 = mergedList;
    while (pointer1 !== null && pointer2 !== null) {
        var value;
        if (pointer1.val < pointer2.val) {
            value = pointer1.val;
            pointer1 = pointer1.next;
        } else {
            value = pointer2.val;
            pointer2 = pointer2.next;
        }
        pointer3.next = new ListNode(value, null);
        pointer3 = pointer3.next;
    }
    while (pointer1 !== null) {
        pointer3.next = new ListNode(pointer1.val, null);
        pointer3 = pointer3.next;
        pointer1 = pointer1.next;
    }
    while (pointer2 !== null) {
        pointer3.next = new ListNode(pointer2.val, null);
        pointer3 = pointer3.next;
        pointer2 = pointer2.next;
    }
    return mergedList.next;
};