单链表插入删除和访问元素代码c++

以下是单链表的插入、删除和访问元素的 C++ 代码：

#include <iostream>
using namespace std;

// 定义链表节点
struct ListNode {
    int val;
    ListNode *next;
    ListNode(int x) : val(x), next(NULL) {}
};

// 插入节点
void insertNode(ListNode *&head, int val) {
    ListNode *newNode = new ListNode(val);
    if (head == NULL) {
        head = newNode;
    } else {
        ListNode *cur = head;
        while (cur->next != NULL) {
            cur = cur->next;
        }
        cur->next = newNode;
    }
}

// 删除节点
void deleteNode(ListNode *&head, int val) {
    if (head == NULL) {
        return;
    }
    if (head->val == val) {
        ListNode *tmp = head;
        head = head->next;
        delete tmp;
    } else {
        ListNode *cur = head;
        while (cur->next != NULL && cur->next->val != val) {
            cur = cur->next;
        }
        if (cur->next != NULL) {
            ListNode *tmp = cur->next;
            cur->next = tmp->next;
            delete tmp;
        }
    }
}

// 访问节点
int getVal(ListNode *head, int index) {
    if (head == NULL) {
        return -1;
    }
    ListNode *cur = head;
    while (index > 0 && cur->next != NULL) {
        cur = cur->next;
        index--;
    }
    if (index == 0) {
        return cur->val;
    } else {
        return -1;
    }
}

int main() {
    ListNode *head = NULL;
    // 插入节点
    insertNode(head, 1);
    insertNode(head, 2);
    insertNode(head, 3);
    insertNode(head, 4);
    insertNode(head, 5);
    // 删除节点
    deleteNode(head, 3);
    deleteNode(head, 5);
    // 访问节点
    cout << getVal(head, 0) << endl; // 输出 1
    cout << getVal(head, 1) << endl; // 输出 2
    cout << getVal(head, 2) << endl; // 输出 4
    return 0;
}