C++实现单链表的插入删除

单链表的插入删除可以通过以下代码实现：

#include <iostream>
using namespace std;

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

// 在链表头插入节点
ListNode* insertAtHead(ListNode* head, int val) {
    ListNode* node = new ListNode(val);
    node->next = head;
    return node;
}

// 在链表尾插入节点
ListNode* insertAtTail(ListNode* head, int val) {
    ListNode* node = new ListNode(val);
    if (head == NULL) {
        head = node;
    } else {
        ListNode* cur = head;
        while (cur->next != NULL) {
            cur = cur->next;
        }
        cur->next = node;
    }
    return head;
}

// 在链表中删除节点
ListNode* deleteNode(ListNode* head, int val) {
    if (head == NULL) {
        return NULL;
    } else if (head->val == val) {
        ListNode* newHead = head->next;
        delete head;
        return newHead;
    } else {
        ListNode* cur = head;
        while (cur->next != NULL && cur->next->val != val) {
            cur = cur->next;
        }
        if (cur->next != NULL) {
            ListNode* temp = cur->next;
            cur->next = cur->next->next;
            delete temp;
        }
        return head;
    }
}

// 打印链表
void printList(ListNode* head) {
    ListNode* cur = head;
    while (cur != NULL) {
        cout << cur->val << " ";
        cur = cur->next;
    }
    cout << endl;
}

int main() {
    ListNode* head = NULL;

    // 在链表头插入节点
    head = insertAtHead(head, 1);
    head = insertAtHead(head, 2);
    head = insertAtHead(head, 3);
    printList(head); // 3 2 1

    // 在链表尾插入节点
    head = insertAtTail(head, 4);
    head = insertAtTail(head, 5);
    head = insertAtTail(head, 6);
    printList(head); // 3 2 1 4 5 6

    // 在链表中删除节点
    head = deleteNode(head, 3);
    head = deleteNode(head, 6);
    printList(head); // 2 1 4 5

    return 0;
}