C++PrimerPlus第六版第十二章类和动态内存分配编程练习答案

1.

Cow.h

#ifndef Cow_H_
#define Cow_H_
#include<iostream>
using std::cout;
using std::endl;
class Cow {
private:
	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;
};
Cow::Cow()
{
	strcpy_s(name, 20, "helloWorld!");
	hobby = nullptr;
	weight = 0.0;
}
Cow::Cow(const char * nm, const char * ho, double wt)
{
	strcpy_s(name,20,nm);
	int len = strlen(ho);
	hobby = new char[len + 1];
	strcpy_s(hobby, len + 1,ho);
	weight = wt;


}
Cow::Cow(const Cow & c)
{
	strcpy_s(name, 20,c.name);
	int len = strlen(c.hobby);
	hobby = new char[len + 1];
	strcpy_s(hobby, len + 1, c.hobby);
	weight = c.weight;
}
Cow::~Cow()
{
	delete[]hobby;
}
Cow & Cow::operator = (const Cow & c)
{
	if (this == &c)
	{
		return *this;
	}
	delete[] hobby;
	strcpy_s(name,20, c.name);
	int len = strlen(c.hobby);
	hobby = new char[len + 1];
	strcpy_s(hobby, len + 1, c.hobby);
	weight = c.weight;
	return  *this;
}
void Cow::ShowCow() const
{
	cout << "name: " << name << '\n'
		<< "hobby: " << hobby << '\n'
		<< "weight: " << weight << endl;
}
#endif // Cow_H_

main.cpp

#include "Cow.h"

int main()
{
	Cow a;
	Cow b("jack", "study", 120);
	b.ShowCow();
	a = b;
	a.ShowCow();
	Cow c(a);
	c.ShowCow();
	return 0;
}

2.

String.h

#ifndef STRING2_H_H
#define STRING2_H_H

#define _CRT_SECURE_NO_WARNINGS
#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; }

	String & operator= (const String &);
	String & operator= (const char *);
	char & operator[] (int i);
	const char & operator[](int i) const;
	friend bool operator<(const String & st, const String &st2);
	friend bool operator>(const String & st, const String &st2);
	friend bool operator==(const String & st, const String &st2);
	friend ostream & operator<<(ostream & os, const String & st);
	friend istream & operator>>(istream & is, String & st);
	static int Howmany();


	friend String operator+(const char * s, const String & st);
	friend String operator+(const String & st, const String &st1);


	void stringlow();
	void stringup();
	int count(char);
};

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;
}
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;
}
String operator+(const char * s, const String & st)
{
	int i = strlen(s) + st.len;
	char *temp = new char[i + 1];
	std::strcpy(temp, s);
	std::strcat(temp, st.str);
	temp[i] = '\0';
	return String(temp);
}

String operator+(const String & st, const String &st1)
{
	int i = st.len + st1.len;
	char *temp = new char[i + 1];
	std::strcpy(temp, st.str);
	std::strcat(temp, st1.str);
	temp[i] = '\0';
	return String(temp);
}
void String::stringlow()
{
	for (int i = 0; i < len + 1; ++i)
		str[i] = tolower(str[i]);
}
void String::stringup()
{
	for (int i = 0; i < len + 1; ++i)
		str[i] = toupper(str[i]);

}
int String::count(char a)
{
	int n = 0;
	for (int i = 0; i < len + 1; ++i)
		if (str[i] == a)
			++n;
	return n;
}
#endif // STRING2_H_H

#include "String.h"
#include <iostream>
using namespace std;
int main()
{
	String s1(" and I am a c++ student.");
	String s2 = "Please enter your name: ";
	String s3;
	String s4("asd");
	cout << s2;
	cin >> s3;
	s2 = "My name is " + s3;
	cout << s2 << ".\n";
	s2 = s2 + s1;
	s2.stringup();
	cout << "The string\n" << s2 << "\ncontains " << s2.count('A')
		<< " 'A' characters int 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.stringlow();
		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;
}

3.

Stock.h

#ifndef STOCK20_H_
#define STOCK20_H_
#define _CRT_SECURE_NO_WARNINGS
#include<iostream>
#include<cstring>
using std::cin;
using std::cout;
using std::ostream;
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 * s, long n = 0, double pr = 0.0);
	~Stock();
	void buy(long num, double price);
	void sell(long num, double price);
	void updata(double price);
	friend ostream & operator<<(ostream & os, const Stock &s);
	const Stock & topval(const Stock & s) const;
};

Stock::Stock()
{
	company = nullptr;
	shares = 0;
	share_val = 0.0;
	total_val = 0.0;
}
Stock::Stock(const char * s, long n, double pr)
{
	int i = strlen(s);
	company = new char[i + 1];
	strcpy(company, s);
	if (n < 0)
	{
		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()
{
	delete[]company;
}
void Stock::buy(long num, double price)
{
	if (num < 0)
	{
		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)
{
	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::updata(double price)
{
	share_val = price;
	set_tot();
}
const Stock & Stock::topval(const Stock & s) const
{
	if (s.total_val > total_val)
		return s;
	else
		return *this;
}
ostream & operator<<(ostream & os, const Stock &s)
{
	using std::ios_base;
	ios_base::fmtflags orig =
		os.setf(ios_base::fixed, ios_base::floatfield);
	std::streamsize prec = os.precision(3);
	os << "company: " << s.company
		<< "  shares: " << s.shares << '\n';
	os << " share Price: $" << s.share_val;
	os.precision(2);
	os << " Total Worth: $" << s.total_val << '\n';
	os.setf(orig, ios_base::floatfield);
	os.precision(prec);
	return os;
}
#endif

main.cpp

#include "Stock.h"
const int STKS = 4;
int main()
{
	Stock stocks[STKS] = {
		Stock("NanoSmart", 12, 20.0),
		Stock("Boffo objects", 200, 2.0),
		Stock("Monolithic Obelistks", 130, 3.25),
		Stock("Fleep Enterprises", 60, 6.5)
	};
	std::cout << "Stock holdings:\n";
	int st;
	for (st = 0; st < STKS; st++)
		std::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";
	std::cout << *top;
	return 0;
}

4.

Stack.h

#ifndef STACK_H_
#define STACK_H__
#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);
};
Stack::Stack(int n)
{
	pitems = new Item[n];
	Size = n;
	top = 0;
}
Stack::Stack(const Stack & st)
{
	pitems = new Item[st.Size];
	Size = st.Size;
	top = st.top;
	for (int i = 0; i < top; i++)
		pitems[i] = st.pitems[i];
}
Stack::~Stack()
{
	delete[] pitems;

}
bool Stack::isempty() const
{
	return top == 0;
}
bool Stack::isfull() const
{
	return top == Size;
}
bool Stack::push(const Item & item)
{
	if (isfull())
		return false;
	else
		pitems[top++] = item;
	return true;
}
bool Stack::pop(Item & item)
{
	if (isempty())
		return false;
	else
		item = pitems[--top];
	return true;
}
Stack &Stack::operator=(const Stack & st)
{
	if (this == &st)
		return *this;
	delete[] pitems;
	pitems = new Item[st.Size];
	Size = st.Size;
	top = st.top;
	for (int i = 0; i < top; ++i)
		pitems[i] = st.pitems[i];
	return *this;
}
#endif

Stack.h

#include "Stack.h"
using std::cout;
int main()
{
	Stack s(5);
	Stack s1(5);
	s.push(100);
	s.push(200);
	s1 = s;
	Stack s3(s);
	Item a, b;
	s1.pop(a);
	s1.pop(b);
	cout << a << " " << b << '\n';
	s3.pop(a);
	s3.pop(b);
	cout << a << " " << b << '\n';
	return 0;
}

5.

Queue.h

#ifndef QUEUE_H_
#define QUEUE_H_
#include <cstdlib>
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);
};

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;
	else
		rear->next = add;
	rear = add;
	return true;
}

bool Queue::dequeue(Item & item)
{
	if (Front == NULL)
		return false;
	item = Front->item;
	items--;
	Node * temp = Front;
	Front = Front->next;
	delete temp;
	if (items == 0)
		rear = NULL;
	return true;
}

void Customer::Set(long when)
{
	processtime = std::rand() % 3 + 1;
	arrive = when;
}
#endif

main.cpp

#include "Queue.h"
#include <cstdlib>
#include <ctime>
#include <iostream>
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: Bank of Heather Automatic Teller\n";
	cout << "Enter maximun size of queue: ";
	int qs;
	cin >> qs;
	Queue line(qs);
	cout << "Enter the average number of simulation hours: ";
	int hours;
	cin >> hours;
	long cyclelimit = MIN_PER_HR * hours;
	cout << "Enter the average number of customers 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;
	int wait_time = 0;
	long line_wait = 0;

	long turnaways1 = 0;
	long customers1 = 0;
	long served1 = 0;
	long sum_line1 = 0;
	int wait_time1 = 0;
	long line_wait1 = 0;
	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 << "        turnaway:   " << 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";
	cout << "Done!\n";

	return 0;
}
bool newcustomer(double x)
{
	return (std::rand() * x / RAND_MAX < 1);
}