7-6 数据结构实验之链表七：单链表中重复元素的删除 (20 分)

这里给出单链表中删除重复元素的实现代码：

class ListNode:
    def __init__(self, val=0, next=None):
        self.val = val
        self.next = next

def deleteDuplicates(head: ListNode) -> ListNode:
    if not head:
        return head
    
    dummy = ListNode(-1)
    dummy.next = head
    
    pre, curr = dummy, head
    while curr:
        if curr.next and curr.next.val == curr.val:
            # 如果当前节点的下一个节点与当前节点值相等，则一直往后遍历，直到不相等
            while curr.next and curr.next.val == curr.val:
                curr = curr.next
            curr = curr.next
            pre.next = curr
        else:
            pre = pre.next
            curr = curr.next
            
    return dummy.next

该算法的时间复杂度为 $O(n)$，空间复杂度为 $O(1)$。