def mergeTwoLists(self, l1, l2):
        dummy = ListNode(0)
        
        cur = dummy
        while l1 != None and l2 != None:
            if l2.val <= l1.val:
                cur.next, cur, l1 = l1, l1, l1.next
            else:
                cur.next, cur, l2 = l2, l2, l2.next
                
        if l1 != None:
            cur.next = l1
        if l2 != None:
            cur.next = l2
            
        return dummy.next
dataset/ETHPy150Open kamyu104/LeetCode/Python/sort-list.py/Solution.mergeTwoLists/swapped operands of `<=`