类和动态内存分配的课后习题（C++ prime plus)

第一题

1. 对于下面的类声明：

class Cow {

char name[20];

char *hobby;

double weight;

public:

Cow();

Cow(const char * nm, const char * ho, double wt);

Cow(const Cow c&);

~Cow();

Cow & operator=(const Cow & c);

void ShowCow() const; // display all new data

};

给这个类提供实现，并编写一个使用所有成员函数的小程序。
Cow.h

#ifndef COW_H_

#define COW_H_

class Cow

{

    private:

        char name[20];

        char * hobby;

        double weght;

    public:

        Cow();

        Cow(const char * nm,const char *ho,double wt);

        Cow(const Cow &c);

        ~Cow();

        Cow  &operator=(const Cow & c);

        void ShowCow()const;

};

#endif

Cow.cpp

#include <iostream>

#include <cstring>

#include "Cow.h"

using namespace std;

Cow::Cow()

{

    strcpy(name,"whp");

    hobby=new char [4];

    strcpy(hobby,"math");

    weght=0.0;

}

Cow::Cow(const char * nm,const char * ho,double wt)

{

    strcpy(name,nm);

    hobby=new char [strlen(ho)+1];

    strcpy(hobby,ho);

    weght=wt;

}

Cow::Cow(const Cow & c)

{

    hobby=new char [strlen(c.hobby)+1];

    strcpy(hobby,c.hobby);

    strcpy(name,c.name);

    weght=c.weght;

}

Cow::~Cow()

{

    delete [] hobby;

}

Cow & Cow::operator=(const Cow & c)

{

    delete [] hobby;

    hobby=new char [strlen(c.hobby)+1];

    strcpy(hobby,c.hobby);

    weght=c.weght;

    strcpy(name,c.name);

    return *this;

}

void Cow::ShowCow()const

{

    cout<<"name:  "<<name<<endl;

    cout<<"hobby: "<<hobby<<endl;

    cout<<"weght: "<<weght<<endl;

    cout<<"end"<<endl;

}

UserCow.cpp

#include <iostream>

#include "Cow.h"

using namespace std;

int main()

{

    Cow mycow;

    mycow.ShowCow();

    Cow mycow1("wer","china",20);

    mycow1.ShowCow();

    Cow mycow2;

    mycow2=mycow;

    mycow2.ShowCow();

    cout<<"结束"<<endl;

    return 0;

}

第二题

通过完成下面的工作来改进String类声明（即将String1.h升级为String2.h）。

a. 对+运算符进行重载，使之可将两个字符串合并成1个。

b. 提供一个Stringlow()成员函数，将字符串中所有的字母字符转换为小写（别忘了cctype系列字符函数）。

c. 提供String()成员函数，将字符串中所有字母字符转换成大写。

d. 提供一个这样的成员函数，它接受一个char参数，返回该字符在字符串中出现的次数
string.h

#ifndef STRING1_H_

#define STRING1_H_

#include <iostream>

using std::ostream;

using std::istream;

class String

{

private:

    char * str;

    int len;

    static int num_strings;

    static const int CINLIM = 80;

public:

    String(const char * s);

    String();

    String(const String &);

    ~String();

    int length () const { return len; }

    void string_change_low();

    void string_change_up();

    int has(char c);

    String & operator=(const String &);

    String & operator=(const char *);

    String operator+(const String & st)const;

    String operator+(const char * str1)const;

    char & operator[](int i);

    const char & operator[](int i) const;

    friend bool operator<(const String &st, const String &st2);

    friend bool operator>(const String &st1, const String &st2);

    friend bool operator==(const String &st, const String &st2);

    friend String operator+(const char * str1,const String & st);

    friend ostream & operator<<(ostream & os, const String & st);

    friend istream & operator>>(istream & is, String & st);

    static int HowMany();

};

#endif

string.cpp

#include <cstring>

#include "string1.h"

using std::cin;

using std::cout;

#include <cstdlib>

int String::num_strings = 0;

int String::HowMany()

{

    return num_strings;

}

String::String(const char * s)

{

    len = std::strlen(s);

    str = new char[len + 1];

    std::strcpy(str, s);

    num_strings++;

}

String::String()

{

    len = 4;

    str = new char[1];

    str[0] = '\0';

    num_strings++;

}

String::String(const String & st)

{

    num_strings++;

    len = st.len;

    str = new char [len + 1];

    std::strcpy(str, st.str);

}

String::~String()

{

    --num_strings;

    delete [] str;

}

void String::string_change_low()

{

    for(int i=0;i<this->len+1;i++)

    {

        this->str[i]=towlower(this->str[i]);

    }

}

void String::string_change_up()

{

    for(int i=0;i<this->len+1;i++)

    {

        this->str[i]=toupper(this->str[i]);

    }

}

 int String::has(char c)

 {

    int count=0;

    for(int i=0;i<this->len+1;i++)

    {

        if(this->str[i]==c)

        {

            count++;

        }

    }

    return count;

 }

String String::operator+(const String & st)const

{

    int new_len=0;

    new_len=len+st.len;

    char * temp=new char [new_len+1];

    strcpy(temp,str);

    strcpy(temp+len,st.str);

    temp[new_len]='\0';

    return String(temp);

}

String String::operator+(const char * str1)const

{

    int new_len=0;

    new_len=len+strlen(str);

    char *temp=new char [new_len+1];

    strcpy(temp,str);

    strcpy(temp,str1);

    return String(temp);

}

String operator+(const char * str1,const String & st)

{

    return String(str1)+st;

}

String & String::operator=(const String & st)

{

    if (this == &st)

        return *this;

    delete [] str;

    len = st.len;

    str = new char[len + 1];

    std::strcpy(str, st.str);

    return *this;

}

String & String::operator=(const char * s)

{

    delete [] str;

    len = std::strlen(s);

    str = new char[len + 1];

    std::strcpy(str, s);

    return *this;

}

char & String::operator[](int i)

{

    return str[i];

}

const char & String::operator[](int i) const

{

    return str[i];

}

bool operator<(const String &st1, const String &st2)

{

    return (std::strcmp(st1.str, st2.str) < 0);

}

bool operator>(const String &st1, const String &st2)

{

    return st2 < st1;

}

bool operator==(const String &st1, const String &st2)

{

    return (std::strcmp(st1.str, st2.str) == 0);

}

ostream & operator<<(ostream & os, const String & st)

{

    os << st.str;

    return os;

}

istream & operator>>(istream & is, String & st)

{

    char temp[String::CINLIM];

    is.get(temp, String::CINLIM);

    if (is)

        st = temp;

    while (is && is.get() != '\n')

        continue;

    return is;

}

UserString.cpp

#include <iostream>

using namespace std;

#include "string1.h"

int main()

{

    String s1(" and I am a C++ student.");

    String s2 = "Please enter your name: ";

    String s3;

    cout << s2;

    cin >> s3;

    s2 = "My name is " + s3;

    cout << s2 << ".\n";

    s2 = s2 + s1;

    s2.string_change_up();

    cout << "The string\n" << s2 << "\ncontains " << s2.has('A')

         << " 'A' characters in it.\n";

    s1 = "red";

    String rgb[3] = { String(s1), String("green"), String("blue")};

    cout << "Enter the name of a primary color for mixing light: ";

    String ans;

    bool success = false;

    while (cin >> ans)

    {

        ans.string_change_low();

        for (int i = 0; i < 3; i++)

        {

            if (ans == rgb[i])

            {

                cout << "That's right!\n";

                success = true;

                break;

            }

        }

        if (success)

            break;

        else

            cout << "Try again!\n";

    }

    cout << "Bye\n";

    return 0;

}

第三题

新编写程序清单10.7和程序清单10.8描述的Stock类，使之使用动态内存分配的内存，而不是string类对象来存储股票名称。另外，使用重载的operator<<()定义代替show()成员函数。再使用程序清单10.9测试新的定义程序。

Stock20.h

#ifndef STOCK20_H_

#define STOCK20_H_

#include <string>

#include <cstdlib>

#include <cstring>

#include <iostream>

using namespace std;

class Stock

{

private:

    char * company;

    int shares;

    double share_val;

    double total_val;

    void set_tot() { total_val = shares * share_val; }

public:

    Stock();

    Stock(const char * strs, long n = 0, double pr = 0.0);

    ~Stock();

    void buy(long num, double price);

    void sell(long num, double price);

    void update(double price);

    friend ostream & operator<<(ostream & os,const Stock & st);

    const Stock & topval(const Stock & s) const;

};

#endif

Stcok20.cpp

#include <iostream>

#include "stock20.h"

Stock::Stock()

{

    company=new char [strlen("whp")+1];

    strcpy(company,"whp");

    shares = 0;

    share_val = 0.0;

    total_val = 0.0;

}

Stock::Stock(const char * strs, long n, double pr)

{

    int len=strlen(strs);

    company=new char [len+1];

    strcpy(company,strs);

    if (n < 0)

    {

        std::cout << "Number of shares can’t be negative; "

                    << company << " shares set to 0.\n";

        shares = 0;

    }

    else

        shares = n;

    share_val = pr;

    set_tot();

}

Stock::~Stock()

{

}

void Stock::buy(long num, double price)

{

     if (num < 0)

    {

        std::cout << "Number of shares purchased can’t be negative. "

             << "Transaction is aborted.\n";

    }

    else

    {

        shares += num;

        share_val = price;

        set_tot();

    }

}

void Stock::sell(long num, double price)

{

    using std::cout;

    if (num < 0)

    {

        cout << "Number of shares sold can’t be negative. "

             << "Transaction is aborted.\n";

    }

    else if (num > shares)

    {

        cout << "You can’t sell more than you have! "

             << "Transaction is aborted.\n";

    }

    else

    {

        shares -= num;

        share_val = price;

        set_tot();

    }

}

void Stock::update(double price)

{

    share_val = price;

    set_tot();

}

ostream & operator<<(ostream & os,const Stock & st)

{

    using std::ios_base;

    ios_base::fmtflags orig =

        os.setf(ios_base::fixed, ios_base::floatfield);

    std::streamsize prec = os.precision(3);

    os << "Company: " <<st.company

        << " Shares: " <<st.shares << '\n';

    os << " Share Price: $" <<st.share_val;

    os.precision(2);

    os << " Total Worth: $" <<st.total_val <<'\n';

    return os;

}

const Stock & Stock::topval(const Stock & s) const

{

    if (s.total_val > total_val)

        return s;

    else

        return *this;

}

UserStcok.cpp

#include <iostream>

#include "stock20.h"

const int STKS = 4;

int main()

{

    Stock stocks[STKS] = {

        Stock("NanoSmart", 12, 20.0),

        Stock("Boffo Objects", 200, 2.0),

        Stock("Monolithic Obelisks", 130, 3.25),

        Stock("Fleep Enterprises", 60, 6.5)

        };

    std::cout << "Stock holdings:\n";

    int st;

    for (st = 0; st < STKS; st++)

        cout<<stocks[st];

    const Stock * top = &stocks[0];

    for (st = 1; st < STKS; st++)

        top = &top->topval(stocks[st]);

    std::cout << "\nMost valuable holding:\n";

    cout<<*top;

     return 0;

}

第四题

Stack.h

#ifndef STOCK_H_

#define STOCK_H_

using namespace std;

#include <iostream>

typedef unsigned long Item;

class Stack

{

private:

    enum {MAX = 10};

    Item * pitems;

    int size;

    int top;

public:

    Stack(int n = MAX);

    Stack(const Stack & st);

    ~Stack();

    bool isempty() const;

    bool isfull() const;

    bool push(const Item & item); 

    bool pop(Item & item);

    Stack & operator=(const Stack & st);

    friend ostream & operator<<(ostream & os,const Stack & st);

};

#endif

Stack.cpp

#include <iostream>

#include "Stack.h"

Stack::Stack(int n=MAX)

{

    pitems=new Item[n];//分配空间

    for(int i=0;i<n;i++)//初始化数组

    {

        pitems[i]=0;

    }

    top=0;

    size=n;

}

Stack::Stack(const Stack & st)

{

    pitems=new Item[st.size];

    for(int i=0;i<st.size;i++)

    {

        pitems[i]=st.pitems[i];

    }

    top=st.top;

    size=st.size;

}

Stack::~Stack()

{

    delete [] pitems;//释放内存

}

bool Stack::isempty()const

{

    return top==0;

}

bool Stack::isfull()const

{

    return top==MAX;

}

bool Stack::push(const Item & item)

{

    if(top<MAX)

    {

        pitems[top++]=item;

        return true;

    }

    else

    {

        return false;

    }

}

bool Stack::pop(Item & item)

{

    if(top>0)

    {

        item=pitems[--top];

        return true;

    }

    else

    {

        return false;

    }

}

Stack & Stack::operator=(const Stack & st)

{

    if(this==&st)

        return * this;

    delete [] pitems;

    top=st.top;

    size=st.size;

    pitems=new Item[st.size];

    for(int i=0;i<st.size;i++)

    {

        pitems[i]=st.pitems[i];

    }

    return *this;

}

ostream & operator<<(ostream & os,const Stack & st)

{

    for(int i=0;i<st.top;i++)

    {

        os<<st.pitems[i]<<endl;

    }

    return os;

}

UserStack.cpp

#include <iostream>

#include <cctype>

#include "Stack.h"

int main()

{

    using namespace std;

    Stack st;

    char ch;

    unsigned long po;

    cout << "Please enter A to add a purchase order,\n"

        << "P to process a PO, or Q to quit.\n";

    while (cin >> ch && toupper(ch) != 'Q')

    {

        while (cin.get() != '\n')

            continue;

        if (!isalpha(ch))

        {

            cout << '\a';

            continue;

        }

        switch(ch)

        {

            case 'A':

            case 'a': cout << "Enter a PO number to add: ";

                      cin >> po;

                      if (st.isfull())

                          cout << "stack already full\n";

                      else

                          st.push(po);

                      break;

            case 'P':

            case 'p': if (st.isempty())

                          cout << "stack already empty\n";

                      else {

                          st.pop(po);

                          cout << "PO #" << po << " popped\n";

                      }

                      break;

        }

        cout << "Please enter A to add a purchase order,\n"

             << "P to process a PO, or Q to quit.\n";

    }

    Stack st2;

    st2=st;

    cout<<"st2"<<st2<<endl;

    cout << "Bye\n";

    return 0;

}

第五题

Heather银行进行的研究表明，ATM客户不希望排队时间不超过1分钟。使用程序清单12.10中的模拟，找出要使平均等候时间为1分钟，每小时到达的客户数应为多少（试验时间不短于100小时）？

Queue.h

#ifndef STACK_H_

#define STACK_H_

class Customer

{

    private:

        long arrive;

        int processtime;

    public:

        Customer(){arrive=processtime=0;}

        void set(long when);

        long when() const {return arrive;}

        int ptime()const {return processtime;}

};

typedef Customer Item;

class Queue

{

    private:

        struct Node{Item item;struct Node * next;};

        enum {Q_SIZE=10};

        Node * front;

        Node * rear;

        int items;

        const int qsize;

        Queue(const Queue & q):qsize(0){}

        Queue & operator=(const Queue & q){return * this;}

    public:

        Queue(int qs=Q_SIZE);

        ~Queue();

        bool isempty()const;

        bool isfull()const;

        int queuecount()const;

        bool enqueue(const Item & item);

        bool dequeue(Item & item);

};

#endif

customer.cpp

#include <iostream>

#include "Queue.h"

Queue::Queue(int qs):qsize(qs)

{

    front=rear=NULL;

    items=0;

}

Queue::~Queue()

{

    Node * temp;

    while(front!=NULL)

    {

        temp=front;

        front==front->next;

        delete temp;

    }

}

bool Queue::isempty()const

{

    return items==0;

}

bool Queue::isfull()const

{

    return items==qsize;

}

int Queue::queuecount()const

{

    return items;

}

bool Queue::enqueue(const Item & item)

{

    if(isfull())

        return false;

    Node *add=new Node;

    add->item=item;

    add->next=NULL;

    items++;

    if(front==NULL)

        front=add;

    rear->next=add;

    rear=add;

    return true;

}

bool Queue::dequeue(Item & item)

{

    if(isempty())

        return false;

    Node * temp=new Node;

    item=front->item;

    temp=front;

    front=front->next;

    delete temp;

    if(items==0)

    {

        rear=NULL;

    }

    return true;

}

bank.cpp

#include <iostream>

#include "Queue.h"

#include <cstdlib>

#include <ctime>

const int MIN_PER_HR=60;

bool newcustomer(double x);

int main()

{

    using std::cin;

    using std::cout;

    using std::endl;

    using  std::ios_base;

    std::srand(std::time(0));

    cout<<"Case Study:Band of Heather Automatic Teller\n";

    cout<<"Enter maximum size of queue:";

    int qs;

    cin>>qs;

    Queue line(qs);

    cout<<"Enter the number of simulation hours:";

    int hours;

    cin>>hours;

    long cyclelimit=MIN_PER_HR*hours;

    cout<<"Enter the average number of customer per hour:";

    double perhour;

    cin>>perhour;

    double min_per_cust;

    min_per_cust=MIN_PER_HR/perhour;

    Item temp;

    long turnaways=0;

    long customers=0;

    long served=0;

    long sum_line=0;

    long wait_time=0;

    long line_wait=0;

    double avetime=0;

    while(perhour++&&avetime<=1)

    {

        while(!line.isempty())

        {

            line.dequeue(temp);

        }

    for(int cycle=0;cycle<cyclelimit;cycle++)

    {

        if(newcustomer(min_per_cust))

        {

            if(line.isfull())

                turnaways++;

            else

            {

                customers++;

                temp.set(cycle);

                line.enqueue(temp);

            }

        }

        if(wait_time<0&&line.isempty())

        {

            line.dequeue(temp);

            wait_time=temp.ptime();

            line_wait+=cycle-temp.when();

            served++;

        }

        if(wait_time>0)

            wait_time--;

        sum_line+=line.queuecount();

    }

    if (customers > 0)

    {

        cout << "customers accepted: " << customers << endl;

        cout << " customers served: " << served << endl;

        cout << " turnaways: " << turnaways << endl;

        cout << "average queue size: ";

        cout.precision(2);

        cout.setf(ios_base::fixed, ios_base::floatfield);

        cout << (double) sum_line / cyclelimit << endl;

        cout << " average wait time: "

             << (double) line_wait / served << " minutes\n";

    }

    else

        cout << "No customers!\n";

    avetime=(double)line_wait/served;

    }

    cout<<"When there comes"<<perhour<<"people per hour,the average wait time will be about 1 inutes.\n"<<endl;

    cout<<"Done";

    return 0;

}

bool newcustomer(double x)

{

    return (std::rand() * x / RAND_MAX < 1);

}

巴特西

类和动态内存分配的课后习题（C++ prime plus)

最新文章

热门文章