手写单链表（基础）

手写了一个单链表，实现了一些简单的功能。

#pragma once

using namespace std;

class Node
{
public:
    Node* next;
    int data;
};

class List
{
private:
    Node* head;
    int length;

public:
    List();
    int size();
    bool empty();
    void push_front(int num);
    void push_back(int num);
    bool insert(int pos, int num);
    bool erase(int pos);
    bool find(int num);
    void clear();
    void show();
};

List::List()
{
    head = new Node;
    head->next = nullptr;
    head->data = 0;
    length = 0;
}

int List::size()
{
    return length;
}

bool List::empty()
{
    if (length == 0) return true;
    else return false;
}

void List::push_front(int num)
{
    Node* first = head->next;
    Node* pushNode = new Node;
    pushNode->data = num;
    pushNode->next = first;
    head->next = pushNode;
    length++;
}

void List::push_back(int num)
{
    Node* temp = head;
    while (temp->next != nullptr)
    {
        temp = temp->next;
    }
    Node* pushNode = new Node;
    pushNode->data = num;
    pushNode->next = nullptr;
    temp->next = pushNode;
    length++;
}

bool List::insert(int pos, int num)
{
    Node* temp = head;
    int i = 0;
    if (pos < 0 || pos > length) return false;
    while (i < pos && temp->next != nullptr)
    {
        i++;
        temp = temp->next;
    }
    Node* pushNode = new Node;
    pushNode->data = num;
    pushNode->next = temp->next;
    temp->next = pushNode;
    length++;
    return true;
}

bool List::erase(int pos)
{
    Node* temp = head;
    int i = 0;
    if (pos <= 0 || pos > length || length == 0) return false;
    while (i < pos - 1 && temp->next != nullptr)
    {
        i++;
        temp = temp->next;
    }
    Node* q = temp->next;
    temp->next = q->next;
    free(q);
    length--;
    return true;
}

bool List::find(int num)
{
    Node* temp = head->next;
    int i = 1;
    while (temp != nullptr && temp->data != num)
    {
        temp = temp->next;
        i++;
    }
    if (temp == nullptr)
        return -1;
    else 
        return i;
}

void List::clear()
{
    Node* nextNode = head->next;
    while (nextNode != nullptr)
    {
        Node* temp = nextNode->next;
        delete nextNode;
        nextNode = temp;
    }
    length = 0;
    head->next = nullptr;
}

void List::show()
{
    if (length == 0) return;
    else
    {
        Node* temp = head->next;
        while (temp->next != nullptr)
        {
            cout << temp->data << " ";
            temp = temp->next;
        }
        cout << temp->data << endl;
    }
}