单链表的基本操作实现

1. 单链表含头结点模型示意图如下：

2. 单链表节点结构定义如下：

struct ListNode {
	int val;
	ListNode* next;
	ListNode(int x) : val(x), next(NULL) {}
};

3. 单链表的基本操作函数如下：

• ListNode* createList(); // 手动输入创建一个链表
• void printList(ListNode* head); // 打印链表数据
• int getListLength(ListNode* head); // 获取链表长度
• ListNode* insertList(ListNode* head, int pos, int data); // 插入数据到链表里
• ListNode* deleteList(ListNode* head, int pos); // 删除链表节点数据

4. 具体代码实现如下：

#include <iostream>

using namespace std;

struct ListNode {
	int val;
	ListNode* next;
	ListNode(int x) : val(x), next(NULL) {}
};

ListNode* createList() {
	ListNode* head = new ListNode(0);    
	ListNode* p = head;    
	ListNode* node = NULL;
	int flag = 1;
	int data = 0;
	while (flag) {
		cout << "Please input the data: " << endl;
		cin >> data;
		if (data != 0) {
			node = new ListNode(data);
			p->next = node;
			p = node;
		}
		else {
			flag = 0;
		}
	}
	return head;
}

void printList(ListNode* head) {
	if (head == NULL || head->next == NULL) {
		cout << "The list is empty!" << endl;
		return;
	} 
	ListNode* p = head->next;
	cout << "The list values are as follows: " << endl;
	while (p != NULL) {
		cout << p->val << " ";
		p = p->next;
	}
	cout << endl;
}

int getListLength(ListNode* head) {
	if (head == NULL || head->next == NULL) {
		cout << "The list is empty!" << endl;
		return 0;
	}
	ListNode* p = head->next;
	int len = 0;
	while (p != NULL) {
		len++;
		p = p->next;
	}
	return len;
}

ListNode* insertList(ListNode* head, int pos, int data) {
	if (pos <= 0) {
		cout << "The pos is error!" << endl;
		return head;
	}
	if (head == NULL) {
		head = new ListNode(0);
	}
	ListNode* p = head;
	int index = 1;
	while (p != NULL && index < pos) {
		p = p->next;
		index++;
	}
	ListNode* node = new ListNode(data);
	if (p != NULL) {
		node->next = p->next;
		p->next = node;
	}
	return head;
}

ListNode* deleteList(ListNode* head, int pos) {
	if (pos <= 0) {
		cout << "The pos is error!" << endl;
		return head;
	}
	if (head == NULL || head->next == NULL) {
		cout << "The list is empty!" << endl;
		return head;
	}
	ListNode* p = head;
	int index = 1;
	while (p != NULL && index < pos) {
		p = p->next;
		index++;
	}
	if (p != NULL && p->next != NULL) {
		ListNode* temp = p->next;
		p->next = temp->next;
		delete temp;
	}
	return head;
}

int main() {
	ListNode* head = NULL;
	head = createList();
	printList(head);
	insertList(head, 3, 300);
	printList(head);
	deleteList(head, 5);
	printList(head);
	cout << "The length of the list is " << getListLength(head) << endl;
	system("pause");
	return 0;
}

5. 运行结果截图如下：