参考：https://blog.csdn.net/ABABC1234/article/details/131329837

删除有序链表中重复的元素，比如
输入链表1，2，2，3，3，4。输出链表1，4
输入链表1，1，2，3，4，4，输出链表2，3

#include <stdio.h>
#include <stdlib.h>

typedef struct Node {
	int data;
	struct Node* next;
} Node, *LinkedList;

// 创建一个新节点
Node* createNode(int data) {
	Node* newNode = (Node*)malloc(sizeof(Node));
	if (newNode == NULL) {
		printf("Error! Unable to create a new node.\n");
		exit(0);
	}
	newNode->data = data;
	newNode->next = NULL;
	return newNode;
}

// 在链表末尾添加新节点
void append(LinkedList* head, int data) {
	if (*head == NULL) {
		*head = createNode(data);
	}
	else {
		Node* lastNode = *head;
		while (lastNode->next != NULL) {
			lastNode = lastNode->next;
		}
		lastNode->next = createNode(data);
	}
}

// 打印链表
void printList(LinkedList head) {
	while (head != NULL) {
		printf("%d ", head->data);
		head = head->next;
	}
	printf("\n");
}

LinkedList deleteDuplicate(Node* head)
{
	if (head == NULL || head->next == NULL)
	{
		return head;
	}
	Node* newHead = NULL;	
	newHead = (Node*)malloc(sizeof(Node));  //创建一个节点，可能第一个就相同
	newHead->next = head;
	Node* cur = head;
	Node* pre = newHead;

	while (cur != NULL)
	{
		bool duplicated = false;
		while (cur->next != NULL && cur->data == cur->next->data)
		{
			duplicated = true;
			Node *temp = cur;
			cur = cur->next;
			free(temp);
		}
		if (duplicated)
		{
			pre->next = cur->next;
			Node *temp = cur;
			cur = cur->next;
			free(temp);
		}
		else
		{
			pre = cur;
			cur = cur->next;
		}
	}
	Node *ret = newHead->next;
	free(newHead);
	return ret;
}

int main() {
	LinkedList head1 = NULL;
	append(&head1, 1);
	append(&head1, 1);
	append(&head1, 3);
	append(&head1, 4);
	append(&head1, 4);
	append(&head1, 5);
	append(&head1, 6);

	printf("Original List1: ");
	printList(head1);

	LinkedList head = deleteDuplicate(head1);

	printf("deleteDuplicate List: ");
	printList(head);
	system("pause");
	return 0;
}