数据结构_单链表的创建

1、尾插法

    （1）不带头结点

typedef int ElementType;
typedef struct Node *List;

struct Node {
	ElementType data;
	struct Node *next;
};


List Create() {

	List ptrL = NULL, s = NULL, tail = NULL;

	int n;
	printf("输入要创建的元素个数：");
	scanf("%d", &n);

	ElementType val;
	for (int i = 0; i < n; i++) {
		printf("请输入第 %d 个元素：", i + 1);
		scanf("%d", &val);

		s = (List)malloc(sizeof(struct Node));
		s->data = val;
		s->next = NULL;

		if (i == 0) ptrL = s;
		else tail->next = s;
		tail = s;
	}

	return ptrL;
}

    （2）带头结点

List Create() {

	//创建头结点
	List ptrL = NULL, s = NULL, tail = NULL;
	ptrL = (List)malloc(sizeof(struct Node));
	if (!ptrL) return NULL;
	ptrL->next = NULL;

	int n;
	printf("输入要创建的元素个数：");
	scanf("%d", &n);

	ElementType val;
	for (int i = 0; i < n; i++) {
		printf("请输入第 %d 个元素：", i + 1);
		scanf("%d", &val);

		s = (List)malloc(sizeof(struct Node));
		s->data = val;
		s->next = NULL;

		if (i == 0) ptrL->next = s;
		else tail->next = s;
		//保存尾节点的位置
		tail = s;			
	}
	return ptrL;
}

2、头插法

    （1）不带头结点

List Create() {


	List ptrL = NULL, s = NULL;

	int n;
	printf("输入要创建的元素个数：");
	scanf("%d", &n);

	ElementType val;
	for (int i = 0; i < n; i++) {
		printf("请输入第 %d 个元素：", i + 1);
		scanf("%d", &val);

		s = (List)malloc(sizeof(struct Node));
		s->data = val;
		s->next = NULL;

		s->next = ptrL;
		ptrL = s;
	}
	return ptrL;
}

    （2）带头结点

List Create() {


	List ptrL = NULL, s = NULL; 
	ptrL = (List)malloc(sizeof(struct Node));
	if (ptrL == NULL) return NULL;
	memset(ptrL, 0, sizeof(struct Node));
	ptrL->next = NULL;

	int n;
	printf("输入要创建的元素个数：");
	scanf("%d", &n);

	ElementType val;
	for (int i = 0; i < n; i++) {
		printf("请输入第 %d 个元素：", i + 1);
		scanf("%d", &val);

		s = (List)malloc(sizeof(struct Node));
		s->data = val;
		s->next = NULL;

		s->next = ptrL->next;
		ptrL->next = s;
	}
	return ptrL;
}

写这篇博文的目的在于，对比 带和不带头结点 的尾插法或头插法，看有什么区别。区别仅在于是否带有头结点，思路是完全一样的！