[못풀었다/javascript/릿코드] merge two sorted lists

const mergeTwoLists = (list1, list2) => {
    // initialize new linked list
    let head = new ListNode(null)

    // new pointer
    let current = head

    // loop while both lists are not null (did not reach end)
    while (list1 && list2) {

        // check which val is lower and point current to it
        // move the pointer on the lower list 
        if (list1.val <= list2.val){
            current.next = list1
            list1 = list1.next
        } else {
            current.next = list2
            list2 = list2.next
        }

        // move the current pointer
        current = current.next
    }

    // determine which node is not null
    let remaining = list1 || list2

    // set current to the remaining list
    current.next = remaining


    // return next because head was initialized to null
    return head.next
};

 

const mergeTwoLists = (list1, list2) => {
    // initialize new linked list
    let head = new ListNode(null)

    // new pointer
    let current = head

    // loop while both lists are not null (did not reach end)
    while (list1 && list2) {

        // check which val is lower and point current to it
        // move the pointer on the lower list 
        if (list1.val <= list2.val){
            current.next = list1
            list1 = list1.next
        } else {
            current.next = list2
            list2 = list2.next
        }

        // move the current pointer
        current = current.next
    }

    // determine which node is not null
    let remaining = list1 || list2

    // set current to the remaining list
    current.next = remaining


    // return next because head was initialized to null
    return head.next
};