c++ Primer Plus（第六版）第十二章习题，写代码之路

c++ Primer Plus（习题12.1)

//12.1头文件#pragma once#ifndef COW_H#define COW_H#include<iostream>#include<cstring>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);//复制构造函数~Cow();Cow&operator=(const Cow&c);void ShowCow()const;};#endif // !COW_H

#include"cow.h"Cow::Cow(){name[0] = '\0';hobby = new char[1];hobby[0] = '\0';//为了与后面析构函数的delete配套,nullptr为空指针新关键字weight = 0.0;}Cow::Cow(const char* nm, const char *ho, double wt){std::strcpy(name, nm);hobby = new char[std::strlen(ho) + 1];std::strcpy(hobby, ho);weight = wt;}Cow::Cow(const Cow&c)//复制构造函数{std::strcpy(name, c.name);hobby = new char[std::strlen(c.hobby) + 1];std::strcpy(hobby, c.hobby);weight = c.weight;}Cow::~Cow(){delete [] hobby;}Cow& Cow::operator=(const Cow&c){if (this == &c)return *this;delete[] hobby;//删除指针再指向的内存hobby = new char[std::strlen(c.hobby) + 1];std::strcpy(name, c.name);std::strcpy(hobby, c.hobby);weight = c.weight;return *this;//this为对象指针，值向调用对象}void Cow::ShowCow()const{std::cout << "Name: " << name << std::endl<< "Hobby: " << hobby << std::endl<< "Weight: " << weight << std::endl;}

c++ Primer Plus（习题12.2)

//自己的string 类，顺便做题目#pragma once#ifndef MYSTRING_H#define MYSTRING_H#include<iostream>using std::ostream;using std::istream;class String{private:char *str;int len;static int num_strings;   //静态类成员static const int CINLIMN = 80;//字符串的最大值public://构造函数和其它方法String(const char*s);String();~String();String(const String &s);//复制构造函数int length()const { return len; }//运算符重载String operator+(const String&s)const;//合并String operator+(const char*);//合并String& operator=(const String&s);String&operator=(const char*);//字符串赋值char &operator[](int i);//重载[]运算符,给字符串某位置赋值const char&operator[](int i)const;String &stringlow();//把字符串变成小写String &stringup();int has(char a);//记录字符出现次数//友元函数friendString operator+(char *st, const String&s);//重载一个字符串与string合并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);//静态成员函数，智能使用静态类成员static int HowMaxny();};#endif // !MYSTRING_H

#include<cctype>#include<cstring>#include"mystring.h"using std::cout;using std::cin;//初始化静态类成员int String::num_strings = 0;//静态类方法int String::HowMaxny(){return num_strings;}//成员方法String::String(const char*s){len = 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 &s){num_strings++;len = s.len;str = new char[len + 1];std::strcpy(str, s.str);}String::~String(){--num_strings;delete[] str;}//重载的运算符方法//将string对象复制给string对象String& String::operator=(const String&s){if (this == &s)return *this;delete[]str;len = s.len;str = new char[len + 1];std::strcpy(str, s.str);return *this;}//将字符串复制给对象String& String::operator=(const char*z){delete[]str;len = strlen(z);str = new char[len + 1];std::strcpy(str, z);return *this;}//重载加号使字符串合并，与string合并String String::operator+(const String&s)const{String temp;temp.len = len + s.len;delete[]temp.str;temp.str = new char[temp.len + 1];std::strcpy(temp.str, str);std::strcat(temp.str, s.str);return temp;}//与字符串合并，字符串在后面String String::operator+(const char*s){String temp;temp.len = len + strlen(s);delete[]temp.str;temp.str = new char[temp.len+1];std::strcpy(temp.str, str);std::strcat(temp.str, s);return temp;}//字符串在前面与string对象合并String operator+(char *st, const String&s){String temp;temp.len = strlen(st) + s.len;delete[]temp.str;temp.str = new char[temp.len + 1];std::strcpy(temp.str, st);//问题在这里，strcpy写成strcatstd::strcat(temp.str, s.str);return temp;}//改写字符串中的某个字符char &String::operator[](int i){return str[i];}//只是读string中的某个字符const char &String::operator[](int i)const{return str[i];}bool operator<(const String&st, const String&st2){return (std::strcmp(st.str, st2.str)<0);}bool operator>(const String&st, const String&st2){return st2 < st;//直接换简单粗暴}bool operator==(const String&st, const String&st2){return (std::strcmp(st.str, st2.str)==0);}//把字符串全部变成小写String &String::stringlow()//考虑要不要改变原字符串{int i = 0;while (i<len){str[i] = std::tolower(str[i]);//糊涂了，这里把str的指针地址增加了，导致程序崩溃i++;}return *this;}//把字符串全部变成大写,会改变原字符串 String &String::stringup(){int i = 0;while (i<len){str[i] = std::toupper(str[i]);//糊涂了，这里把str的指针地址增加了，导致程序崩溃i++;//按以前的把str指针增加的量减回去}return *this;}int String::has(char a)//记录字符出现次数{int counts = 0;int i = 0;while (i<len){if (str[i]== a)counts++;i++;}return counts;}ostream&operator<<(ostream&os, const String &st){os << st.str;return os;}istream&operator >> (istream&is, String&st){char temp[String::CINLIMN];is.get(temp, String::CINLIMN);if (is)st = temp;while (is&&is.get() != '\n')continue;return is;}

//书上提供的测试#include<iostream>using namespace std;#include"mystring.h"int main()                                 {String s1(" and i am a C++ student.");String s2 = "Please enter you name: ";String  s3;cout << s2;cin >> s3;s2 = "My name is "+s3;cout << s2 << ".\n";s2 = s2 + s1;s2.stringup();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 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;elsecout << "Try again!\n";}cout << "Bye!\n";return 0;}

c++ Primer Plus（习题12.3)

//stock.h  #ifndef STOCK_H_  #define STOCK_H_  #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 *co, long n = 0, double pr = 0.0);Stock(const Stock &);~Stock();void buy(long num, double price);void sell(long num, double price);void update(double price);const Stock & topval(const Stock & s)const;Stock & operator=(const Stock & s);friend ostream & operator<<(ostream & os, const Stock & s);};#endif

#include<iostream>  #include "stock.h"  Stock::Stock() {company = new char[8];strcpy(company, "no name");shares = 0;share_val = 0.0;total_val = 0.0;}Stock::Stock(const char *co, long n, double pr) {int len = strlen(co);company = new char[len + 1];strcpy(company, co);if (n < 0){cout << "Number of shares can't be negative; "<< company << " shares set to 0.\n";shares = 0;}elseshares = n;share_val = pr;set_tot();}Stock::Stock(const Stock & s) {int len = strlen(s.company);company = new char[len + 1];strcpy(company, s.company);shares = s.shares;set_tot();}Stock::~Stock() {delete[] company;}void Stock::buy(long num, double price) {if (num < 0){cout << "Number of shares purchased cannot 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 cannot be negative. " << "Transaction is aborted.\n";}else if (num > shares) {cout << "You cannot 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();}const Stock & Stock::topval(const Stock & s)const {if (s.total_val > total_val)return s;elsereturn *this;}Stock & Stock::operator=(const Stock & s) {int len = strlen(s.company);company = new char[len + 1];strcpy(company, s.company);shares = s.shares;set_tot();return *this;}ostream & operator<<(ostream & os, const Stock & s) {ios_base::fmtflags orig = cout.setf(ios_base::fixed, ios_base::floatfield);streamsize prec = cout.precision(3);cout << "Company: " << s.company << " Shares: " << s.shares << '\n';cout << " Share Price: $" << s.share_val;cout.precision(2);cout << " Total Worth: $" << s.total_val << '\n';cout.setf(orig, ios_base::floatfield);cout.precision(prec);return os;}

//又是熟悉的方法，注意new和delete的配合就行，书上大部分的源码#include <iostream>  #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 Obelisks", 130, 3.25),Stock("Fleep Enterprises", 60, 6.5)};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]);}cout << "\nMost valuable holding:\n";cout << *top;cin.get();return 0;}

c++ Primer Plus（习题12.4)

//stock.h  #ifndef STOCK_H_  #define STOCK_H_  #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 *co, long n = 0, double pr = 0.0);Stock(const Stock &);~Stock();void buy(long num, double price);void sell(long num, double price);void update(double price);const Stock & topval(const Stock & s)const;Stock & operator=(const Stock & s);friend ostream & operator<<(ostream & os, const Stock & s);};#endif

#include<iostream>  #include "stock.h"  Stock::Stock() {company = new char[8];strcpy(company, "no name");shares = 0;share_val = 0.0;total_val = 0.0;}Stock::Stock(const char *co, long n, double pr) {int len = strlen(co);company = new char[len + 1];strcpy(company, co);if (n < 0){cout << "Number of shares can't be negative; "<< company << " shares set to 0.\n";shares = 0;}elseshares = n;share_val = pr;set_tot();}Stock::Stock(const Stock & s) {int len = strlen(s.company);company = new char[len + 1];strcpy(company, s.company);shares = s.shares;set_tot();}Stock::~Stock() {delete[] company;}void Stock::buy(long num, double price) {if (num < 0){cout << "Number of shares purchased cannot 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 cannot be negative. " << "Transaction is aborted.\n";}else if (num > shares) {cout << "You cannot 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();}const Stock & Stock::topval(const Stock & s)const {if (s.total_val > total_val)return s;elsereturn *this;}Stock & Stock::operator=(const Stock & s) {int len = strlen(s.company);company = new char[len + 1];strcpy(company, s.company);shares = s.shares;set_tot();return *this;}ostream & operator<<(ostream & os, const Stock & s) {ios_base::fmtflags orig = cout.setf(ios_base::fixed, ios_base::floatfield);streamsize prec = cout.precision(3);cout << "Company: " << s.company << " Shares: " << s.shares << '\n';cout << " Share Price: $" << s.share_val;cout.precision(2);cout << " Total Worth: $" << s.total_val << '\n';cout.setf(orig, ios_base::floatfield);cout.precision(prec);return os;}

//书上的一个测试程序，觉得赋值运算符没体现出来，复制构造函数也没用。#include<iostream>#include<cctype>#include"stack.h"int main(){using namespace std;char ch;Stack st;unsigned long po;cout << "Please enter A to add a customer name and payment,\n"<< "D to delete a customer,or Q to exit.\n";while (cin >> ch&&toupper(ch) != 'Q'){while (cin.get() != '\n')continue;         //清空多余字符if (!isalpha(ch)){cout << "\a";     //判断是否输入为字母continue;}switch (ch){case 'A':case'a':cout << "Enter a PO number to add: ";cin >> po;if (st.isfull())cout << "stack is full!\n";elsest.push(po);break;case'd':case'D':if (st.isempty())cout << "stack already empty.\n";else{st.pop(po);cout << "PO # " << po << " been delete!\n";}break;}cout << "Please enter A to add a customer name and payment,\n"<< "D to delete a customer,or Q to exit.\n";}cout << "Bye!\n";return 0;}

c++ Primer Plus（习题12.5)

//c++版，书上的源码#pragma once#pragma execution_character_set("utf-8")//本文件为utf-8编码格式#ifndef QUEUE_H_  #define QUEUE_H_  using namespace std;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  

#include"myqueue.h"#include<cstdlib>Queue::Queue(int qs) :qsize(qs) {front = rear = nullptr;items = 0;}Queue::~Queue() {Node *temp;while (front != nullptr) {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 (items == qsize)return false;Node *add = new Node;add->item = item;add->next = nullptr;items++;if (front == nullptr)front = add;elserear->next = add;rear = add;return true;}bool Queue::dequeue(Item &item) {if (items == 0)return false;item = front->item;items--;Node *temp = front;front = front->next;delete temp;if (items == 0)rear = nullptr;return true;}void Customer::set(long when) {processtime = std::rand() % 3 + 1;arrive = when;}

//书上的源码，题目的意思是自己玩他设计的这个程序//来模拟银行挣钱的秘诀，看懂了程序改一下简单，但本人没怎么改，增加了一个队列而已//秘诀就是平均每小时来50个人，等候时间大于200；#include <iostream>  #include <cstdlib>  #include <ctime>  #include "myqueue.h"  const int MIN_PER_HR = 60;bool newcustomer(double x);int main() {srand(time(0));cout << "Case Study: Bank of Heather Automatic Teller\n";cout << "Enter maximum size of queue: ";//最大的排队人数int qs;cin >> qs;Queue line1(qs);Queue line2(qs);cout << "Enter the number of simulation hours: ";//测试的时间int hours;cin >> hours;long cyclelimit = MIN_PER_HR*hours;cout << "Enter the average number of cunstomers per hour: ";//每小时的额客户数double perhour;cin >> perhour;double min_per_cust;min_per_cust = MIN_PER_HR / perhour;//记录总的分钟数Item temp;long turnaways = 0;//拒绝人数long customers = 0;//来的人数long served = 0;//服务人数long sum_line = 0;//队列的长度int wait_time1 = 0;//取款机空闲的等待时间long wait_time2 = 0;long line_wait = 0;//队列的总等待时间for (long cycle = 0; cycle < cyclelimit; cycle++) {if (newcustomer(min_per_cust)){if (line1.isfull() && line2.isfull())turnaways++;else {customers++;temp.set(cycle);if (line1.queuecount() < line2.queuecount())line1.enqueue(temp);elseline2.enqueue(temp);}}if (wait_time1 <= 0 && !line1.isempty()){line1.dequeue(temp);wait_time1 = temp.ptime();line_wait += cycle - temp.when();served++;}if (wait_time2 <= 0 && !line2.isempty()){line2.dequeue(temp);wait_time2 = temp.ptime();line_wait += cycle - temp.when();served++;}if (wait_time1 > 0)wait_time1--;if (wait_time2 > 0)wait_time2--;sum_line += (line1.queuecount() + line2.queuecount()) / 2;}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";}elsecout << "No customers!\n";cout << "Done!\n";return 0;}bool newcustomer(double x) {return (rand()*x / RAND_MAX < 1);}

过年前清完，这个寒假才有意义············