单向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：