C++/QT 1 - 技术栈

题目1:自定义实现字符串类

题目描述：

实现一个简单的自定义字符串类 MyString，要求:

1】支持构造函数、拷贝构造函数、赋值运算符

2】实现基本的字符串操作：长度、拼接、比较

3】实现对MyString对象的输入、输出

4】正确处理内存管理

cpp 复制代码

#include <iostream>
#include <cstring>

using namespace std;

class MyString
{
    friend istream &operator>>(istream &cin, MyString &s);
    friend ostream &operator<<(ostream &cout, const MyString &s);
private:
    char *str;
    size_t length;
public:
    //无参构造函数
    MyString():str(new char[1]), length(0)
    {
        str[0] = '\0';
    }

    //有参构造函数
    MyString(const char *s)
    {
        if(s==nullptr)
        {
            str = new char[1];
            str[0] = '\0';
            length = 0;
        }
        else
        {
            length = strlen(s);
            str = new char[length+1];
            strcpy(str,s);
        }
    }

    //拷贝构造函数
    MyString(const MyString &other)
    {
        length = other.length;
        str = new char[length+1];
        strcpy(str, other.str);
    }

    //赋值
    MyString &operator=(const MyString &other)
    {
        if(this != &other)
        {
            delete[] str;

            length = other.length;
            str = new char[length+1];
            strcpy(str, other.str);
        }
        return *this;
    }

    MyString &operator=(const char *s)
    {
        if(s==nullptr)
        {
            delete[] str;
            length = 0;
            str = new char[1];
            str[0] = '\0';
        }
        else
        {
            delete[] str;
            length = strlen(s);
            str = new char[length+1];
            strcpy(str,s);
        }
        return *this;
    }

    //长度
    size_t size() const
    {
        return length;
    }

    //拼接
    MyString operator+(const MyString &other)
    {
        char *new_str = new char[length+other.length+1];
        strcpy(new_str, str);
        strcat(new_str, other.str);
        MyString result(new_str);
        delete[] new_str;
        return result;
    }

    //比较
    bool operator<(const MyString& other) const
    {
        return strcmp(str, other.str) < 0;
    }
    bool operator>(const MyString& other) const
    {
        return strcmp(str, other.str) > 0;
    }
    bool operator==(const MyString& other) const
    {
        return strcmp(str, other.str) == 0;
    }
    bool operator!=(const MyString& other) const
    {
        return strcmp(str,other.str)!=0;
    }

    //析构函数
    ~MyString()
    {
        delete[] str;
    }

};

//对象的输入
istream &operator>>(istream &cin, MyString &s)
{
    char buf[1024]={0};
    cin>>buf;
    s = MyString(buf);
    return cin;
}

//对象的输出
ostream &operator<<(ostream &cout, const MyString &s)
{
    cout << s.str;
    return cout;
}


int main()
{
    MyString s1;
    MyString s2 = "hello";
    MyString s3 = s2;
    cout << s3 << endl;
    s3 = " world";
    cout << s3 << endl;

    MyString s4;
    s4 = s2+s3;
    cout << s4 << endl;
    if(s1<s2)
    {
        cout << "s1<s2" << endl;
    }
    cout << s4.size() << endl;

    return 0;
}

题目2:智能图书管理系统

题目描述：

实现一个简单的图书管理系统，要求

1】使用类和对象来管理图书

2】每本图书有书名、作者、和库存数量

3】实现添加图书、借书、还书和查询

4】使用STL容器存储图书信息

cpp 复制代码

#include <iostream>
#include <vector>

using namespace std;

class Library
{
    friend void show2(vector<Library> &v);
    friend ostream &operator<<(ostream &cout, const Library &a);
    friend void fun(string a, vector<Library> &v);
    friend void fun2(string a, vector<Library> &v);
    friend void show(vector<Library> &v);
private:
    string name;
    string writer;
    int number;
    static int left;
public:
    Library(){}
    Library(string name, string writer, int number):name(name), writer(writer), number(number)
    {}

    //添加
    void add()
    {
        string n;
        cout << "输入书名：";
        getline(cin, n);
        name = n;
        cout << "输入作者：";
        getline(cin, n);
        writer = n;
        int a;
        cout << "输入添加数量：";
        cin >> a;
        number = a;
        left+=number;
    }

    //借书
    void borrow()
    {
        if(number==0)
        {
            cout << "当前无该图书" << endl;
        }
        if(number>0)
        {
            cout << "允许借书" << endl;
            number--;
            left--;
        }
    }

    //还书
    void send_back()
    {
        number++;
        left++;
        cout << "已送还" << endl;
    }

    //查询
//    void show()
//    {
//        cout <<"书名：" << name << " 作者："<< writer << " 剩余数量：" << number << endl;
//    }

};

int Library::left=0;

ostream &operator<<(ostream &cout, const Library &a)
{
    cout <<"书名：" << a.name << "\t作者："<< a.writer << "\t剩余数量：" << a.number << endl;
    return cout;
}

void show(vector<Library> &v)
    {
        vector<Library>::iterator p;
        for(p=v.begin(); p!=v.end(); p++)
        {
            cout << *p;
        }
        cout << "书库当前一共有：" << Library::left << "本书" << endl;
    }



void fun(string a, vector<Library> &v)
{
    vector<Library>::iterator p;
    for(p=v.begin(); p!=v.end(); p++)
    {
        if(p->name == a)
        {
            p->number++;
            Library::left++;
            cout << "已送还" << endl;
        }
    }
}

void fun2(string a, vector<Library> &v)
{
    vector<Library>::iterator p;
    for(p=v.begin(); p!=v.end(); p++)
    {
        if(p->name == a)
        {
            if(p->number==0)
            {
                cout << "当前无该图书" << endl;
            }
            if(p->number>0)
            {
                cout << "允许借书" << endl;
                p->number--;
                Library::left--;
            }
        }
    }
}

int main()
{
    vector<Library> v;

    int choice=-1;
    while(choice!=5)
    {
        cout << "1.添加" << endl;
        cout << "2.借书" << endl;
        cout << "3.还书" << endl;
        cout << "4.查询" << endl;
        cout << "5.退出" << endl;

        cin >> choice;
        getchar();
        if(choice ==1)
        {
            Library l1;
            l1.add();
            v.push_back(l1);
        }
        if(choice ==2)
        {
            string a;
            cout << "输入书名：";
            getline(cin, a);
            fun2(a, v);
        }
        if(choice ==3)
        {
            string a;
            cout << "输入书名：";
            getline(cin, a);
            fun(a, v);
        }
        if(choice ==4)
        {
            show(v);
        }
    }

    return 0;
}