用C++编写程序完成单链表的建立、查找、插入和删除操作。

好的，下面是一个用C++编写的单链表的例子，包括建立、查找、插入和删除操作的实现：

#include <iostream>

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

// 建立单链表
ListNode* createLinkedList(std::initializer_list<int> values) {
    ListNode* head = NULL;
    ListNode* tail = NULL;
    for (int val : values) {
        ListNode* newNode = new ListNode(val);
        if (head == NULL) {
            head = newNode;
            tail = newNode;
        } else {
            tail->next = newNode;
            tail = newNode;
        }
    }
    return head;
}

// 查找链表中是否存在某个值
bool searchLinkedList(ListNode* head, int target) {
    ListNode* curr = head;
    while (curr != NULL) {
        if (curr->val == target) {
            return true;
        }
        curr = curr->next;
    }
    return false;
}

// 在链表的指定位置插入节点
void insertNode(ListNode*& head, int pos, int val) {
    ListNode* newNode = new ListNode(val);
    if (pos == 0) {
        newNode->next = head;
        head = newNode;
    } else {
        ListNode* curr = head;
        int count = 0;
        while (curr != NULL && count < pos - 1) {
            curr = curr->next;
            count++;
        }
        if (curr != NULL) {
            newNode->next = curr->next;
            curr->next = newNode;
        }
    }
}

// 删除链表中指定位置的节点
void deleteNode(ListNode*& head, int pos) {
    if (pos == 0) {
        ListNode* temp = head;
        head = head->next;
        delete temp;
    } else {
        ListNode* curr = head;
        int count = 0;
        while (curr != NULL && count < pos - 1) {
            curr = curr->next;
            count++;
        }
        if (curr != NULL && curr->next != NULL) {
            ListNode* temp = curr->next;
            curr->next = curr->next->next;
            delete temp;
        }
    }
}

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

int main() {
    // 创建链表 1 -> 2 -> 3 -> 4 -> 5
    ListNode* head = createLinkedList({1, 2, 3, 4, 5});
    printLinkedList(head);

    // 查找链表中是否存在值为 3 的节点
    bool found = searchLinkedList(head, 3);
    std::cout << "Found 3 in the linked list: " << (found ? "true" : "false") << std::endl;

    // 在位置 2 插入值为 6 的节点
    insertNode(head, 2, 6);
    printLinkedList(head);

    // 删除位置 4 的节点
    deleteNode(head, 4);
    printLinkedList(head);

    return 0;
}

这段代码实现了单链表的建立、查找、插入和删除操作。你可以根据需要进行修改和扩展。希望对你有帮助！