[Leetcode] 21. Merge two Sorted Lists java__ merged

    /**21. Merge two Sorted Lists 
     * @param L1
     * @param L2
     * @return Merging two ordered lists/public
    ListNode mergetwolists (Li Stnode L1, ListNode L2) {
        listnode ret = new ListNode ( -1);
        ListNode L = ret;

        while (L1!= null && L2!= null) {
            if (L1.val < L2.val) {
                l.next = L1;
                L1 = L1.next;
            } else {
                l.next = L2;
                L2 = L2.next;
            }

        while (L1!= null) {
            l.next = L1;
            L1 = L1.next;
        }
        while (L2!= null) {
            l.next = L2;
            L2 = L2.next;
        }
        return ret.next;
    }

Improved: Linked list, so do not read each loop

 public ListNode mergetwolists (listnode L1, ListNode L2) {listnode ret = new ListNode
        (-1);
        ListNode rethead = ret;
        if (L1 = = NULL && L2 = null) {return null;
        }else if (L1 = null) {return L2;
        else if (L2 = null) {return L1; 
                while (L1!= null && L2!= null) {if (L1.val <= l2.val) {ret.next = L1;
                L1 = L1.next;
            ret = Ret.next;
                else {ret.next = L2;
                L2 = L2.next;
            ret = Ret.next;
        } if (L1!= null) {ret.next = L1;
        } if (L2!= null) {ret.next = L2;
    return rethead.next; }