//雙向鏈表的結(jié)點(diǎn)，包含一個(gè)數(shù)據(jù)域，兩個(gè)指針域
typedef struct DoublyNode {
	ElementType date;  //數(shù)據(jù)域
	struct DoublyNode* prev;   //指向前綴結(jié)點(diǎn)
	struct DoublyNode* next;   //指向后綴結(jié)點(diǎn)
}DoublyNode;

//雙向鏈表
typedef struct DoublyLinkList {
	int length;
	DoublyNode* next;
};

//雙向鏈表的結(jié)點(diǎn)，包含一個(gè)數(shù)據(jù)域，兩個(gè)指針域
typedef struct DoublyNode {
	ElementType date;  //數(shù)據(jù)域
	struct DoublyNode* prev;   //指向前綴結(jié)點(diǎn)
	struct DoublyNode* next;   //指向后綴結(jié)點(diǎn)
}DoublyNode;
 
//雙向鏈表
typedef struct DoublyLinkList {
	int length;
	DoublyNode* next;
};

void InsertDoublyLinkList(DoublyLinkList* dlist, int pos, ElementType element) {
	//創(chuàng)建空節(jié)點(diǎn)
	DoublyNode* node = (DoublyLinkList*)malloc(sizeof(DoublyLinkList));
	node->date = element;
	node->prev = NULL;
	node->next = NULL;
	//在第一個(gè)位置插入結(jié)點(diǎn)
	if (pos == 1) {
		node->next = dlist->next;
		dlist->next = node;
		node->next->prev = node;
		dlist->length++;
		return;
	}
	DoublyLinkList* currNode = dlist->next;
	for (int i = 1; currNode && i < pos - 1; i++) {
		currNode = currNode->next;
	}
	if (currNode) {
		node->prev = currNode;
		if (currNode->next) {
			//如果前置結(jié)點(diǎn)非空->因?yàn)榭站捅硎緵]有后繼結(jié)點(diǎn)了
			//將插入位置的前置結(jié)點(diǎn)改為指向新結(jié)點(diǎn)
			currNode->next->prev = node;
		}
		node->next = currNode->next;
		currNode->next = node;
		dlist->length++;
	}
}

void DeleteDoublyLinkList(DoublyLinkList* dlist, int pos) {
	if (pos == 1) {
		DoublyLinkList* node = dlist->next;
		if (node) {
			dlist->next;
			if (node->next) {
				//如果喲有第二個(gè)結(jié)點(diǎn)，那么設(shè)置第二個(gè)結(jié)點(diǎn)的前置結(jié)點(diǎn)為NULL
				node->next->prev = NULL;
			}
			free(node);
			dlist->length--;
		}
		return;
	}
 
	DoublyLinkList* node = dlist->next;
	for (int i = 1; i < pos; i++) {
		node = node->next;
	}
	if (node) {
		if (node->next) {
			node->next->prev = node->prve;
		}
		node->prev->next = node->next;
		free(node);
		dlist->length--;
	}
	return;
}