leetcode: 82. Remove Duplicates from Sorted List II

# Given a sorted linked list, delete all nodes that have duplicate numbers,
# leaving only distinct numbers from the original list.
#
# For example,
# Given 1->2->3->3->4->4->5, return 1->2->5.
# Given 1->1->1->2->3, return 2->3.

class ListNode():
    def __init__(self, x):
        self.val = x
        self.next = None

class Solution():
    def deleteDuplicates(self, head):
        pre = dummy = ListNode(0)
        cur = head
        while cur:
            if cur.next and cur.next.val == cur.val:
                val = cur.val
                while cur and cur.val == val:
                    cur = cur.next
                pre.next = cur
            else:
                pre.next, pre, cur = cur, cur, cur.next
        return dummy.next


if __name__ == "__main__":
    head, head.next, head.next.next, head.next.next.next, head.next.next.next.next, head.next.next.next.next.next, head.next.next.next.next.next.next\
        = ListNode(1), ListNode(2), ListNode(3), ListNode(3), ListNode(4), ListNode(4), ListNode(5)
    print(Solution().deleteDuplicates(head))