用c++设计一个带头结点单链表类，实现单链表的创建、输入、输出、插入、删除、查找、销毁等操作

好的，以下是用C++设计的带头结点单链表类的实现：

#include <iostream>
using namespace std;

template <typename T>
class ListNode {
public:
    T data;
    ListNode<T>* next;
    ListNode(T val = 0, ListNode<T>* ptr = nullptr) : data(val), next(ptr) {}
};

template <typename T>
class LinkedList {
private:
    ListNode<T>* head;
public:
    LinkedList() { head = new ListNode<T>; }
    ~LinkedList() { clear(); delete head; }
    void clear();
    bool isEmpty() const { return head->next == nullptr; }
    int length() const;
    bool insert(int i, const T& x);
    bool remove(int i);
    int search(const T& x) const;
    void input();
    void output() const;
};

template <typename T>
void LinkedList<T>::clear() {
    ListNode<T>* p = head->next, *q;
    head->next = nullptr;
    while (p != nullptr) {
        q = p->next;
        delete p;
        p = q;
    }
}

template <typename T>
int LinkedList<T>::length() const {
    ListNode<T>* p = head->next;
    int len = 0;
    while (p != nullptr) {
        len++;
        p = p->next;
    }
    return len;
}

template <typename T>
bool LinkedList<T>::insert(int i, const T& x) {
    if (i < 0) return false;
    ListNode<T>* p = head;
    int j = -1;
    while (p != nullptr && j < i - 1) {
        p = p->next;
        j++;
    }
    if (p == nullptr) return false;
    ListNode<T>* q = new ListNode<T>(x, p->next);
    p->next = q;
    return true;
}

template <typename T>
bool LinkedList<T>::remove(int i) {
    if (i < 0) return false;
    ListNode<T>* p = head;
    int j = -1;
    while (p != nullptr && j < i - 1) {
        p = p->next;
        j++;
    }
    if (p == nullptr || p->next == nullptr) return false;
    ListNode<T>* q = p->next;
    p->next = q->next;
    delete q;
    return true;
}

template <typename T>
int LinkedList<T>::search(const T& x) const {
    ListNode<T>* p = head->next;
    int i = 0;
    while (p != nullptr && p->data != x) {
        p = p->next;
        i++;
    }
    if (p == nullptr) return -1;
    else return i;
}

template <typename T>
void LinkedList<T>::input() {
    clear();
    int n;
    cin >> n;
    for (int i = 0; i < n; i++) {
        T x;
        cin >> x;
        insert(i, x);
    }
}

template <typename T>
void LinkedList<T>::output() const {
    ListNode<T>* p = head->next;
    while (p != nullptr) {
        cout << p->data << " ";
        p = p->next;
    }
    cout << endl;
}