C++ primer plus 第六版 第十六章 编程练习答案

第十六章 编程练习答案

这章看的不仔细，第4,10题完全是看网上的额。感觉第一次看不太熟悉，完全不知道说什么，做完题有点明白STL是什么了。

1.

#include <iostream>
#include <string>
#include <algorithm>

using std::string;
bool judge(const string & str);

int main()
{
    using std::cout;
    using std::endl;
    using std::cin;

    string t1;
    cout << "Please enter the string: ";
    cin >> t1;
    int ans = judge(t1);
    if (ans > 0)
        cout << "true" << endl;
    if (ans == 0)
        cout << "false" << endl;    
    return 0;
}

bool judge(const string & str)
{
    string temp;
    temp = str;
    reverse(temp.begin(), temp.end());//反转函数,直接用
    return temp == str;
}

2.

与第一题基本类似，就是加了一个对字符串的处理

#include <iostream>
#include <string>
#include <algorithm>
#include <cctype>

using std::string;
using std::cout;
using std::endl;
using std::cin;

bool judge(const string & str);
char toLower(char ch) {return tolower(ch); }

int main()
{
    string t1;
    cout << "Please enter the string: ";
    getline(cin, t1);
    int ans = judge(t1);
    if (ans > 0)
        cout << "true" << endl;
    if (ans == 0)
        cout << "false" << endl;    
    return 0;
}

bool judge(const string & str)
{
//对输入字符串进行处理，去掉其他符号，
//全部变为小写后进行比较 
    string temp;
    for (int i = 0; i < (int)str.size(); ++i)
    {
        if ((str[i] >= 'a' && str[i] <= 'z') || (str[i] >= 'A' && str[i] <= 'Z'))
            temp.push_back(tolower(str[i]));//push_back作用是字符串之后插入一个字符
    }
    string s1 = temp;
    reverse(temp.begin(), temp.end());
    return temp == s1;
}

3.

这题用了书上16-2的读取文件的方法，没有用提示给的思路。

#include <iostream>
#include <string>
#include <cstdlib>
#include <ctime>
#include <cctype>
#include <fstream>
#include <cstdlib>

using std::string;
const int NUM = 26;

int main()
{
    using std::cout;
    using std::cin;
    using std::tolower;
    using std::endl;
    std::srand(std::time(0));

//用文件打开字符串
    string wl[NUM];
    std::ifstream fin;
    fin.open("U16p3.txt");
    if (fin.is_open() ==  false)
    {
        std::cerr << "Can't open file. Bye.\n";
        exit(EXIT_FAILURE);
    }       
    string item;
    int count = 0;
    getline(fin, item, ',');//,是分界字符    
    while (fin)
    {
        wl[count] = item;
        getline(fin, item, ',');        
        ++count;
    }
    fin.close();
    const string wordlist[NUM] = wl; 

//后面不用修改    
    char play;
    cout << "Will you play a word game? <y/n>";
    cin >> play;
    play = tolower(play);
    while (play == 'y')
    {
        string target = wordlist[std::rand() % NUM];
        int length = target.length();
        string attempt(length, '-');
        string badchars;
        int guesses = 6;
        cout << "Guess my secret word. It has " << length << " letters, and you guess"
            "\none letter at a time. You get " << guesses << " wrong guesses.\n";
        cout << "Your word: " << attempt << endl;
        while (guesses > 0 && attempt != target)
        {
            char letter;
            cout << "Guess a letter: ";
            cin >> letter;
            if (badchars.find(letter) != string::npos
                || attempt.find(letter) !=string::npos)
            {
                cout << "You already guess that. Try again.\n";
                continue;
            }
            int loc = target.find(letter);
            if (loc == string::npos)
            {
                cout << "Oh, bad guess!\n";
                --guesses;
                badchars += letter;
            }               
            else
            {
                cout << "Good guess!\n";
                attempt[loc] = letter;
                loc = target.find(letter, loc + 1);
                while (loc != string::npos)
                {
                    attempt[loc] = letter;
                    loc = target.find(letter, loc + 1);

                }
            }
            cout << "Your word: " << attempt << endl;   
            if (attempt != target)
            {
                if (badchars.length() > 0)
                    cout << "Bad choices: " << badchars << endl;
                cout << guesses << " bad guesses left\n";
            }   
        }       
        if (guesses > 0)
            cout << "That's right!\n";
        else
            cout << "Sorry, the world is " << target << ".\n";
            cout << "Will you play another? <y/n> ";
            cin >> play;
            play = tolower(play);
    }

    cout << "Bye\n";

    return 0;   
}

4.

#include <iostream>
#include <algorithm>

int reduce(long ar[], int n);
using namespace std;

int main()
{
    long ar[10] = {11, 3, 5, 9, 7, 4, 3, 5, 11, 3};
    cout << "The data: ";
    for (int i = 0; i < 10; ++i) {
        cout << ar[i] << " ";
    }
    cout << endl;
    cout << "After sort and unique: ";    
    int n = reduce(ar, 10);   
    for (int i = 0; i < n; ++i) {
        cout << ar[i] << " ";
    }
    cout << endl;   
    return 0;
}

int reduce(long ar[], int n)
{
    //STL的sort（）和unique（）两个函数
    sort(ar, ar + n);
    long* p = unique(ar, ar + n);
    return (int)(p - ar);
}

5.

#include <iostream>
#include <algorithm>

template <class T>
int reduce(T str[], int n);

using namespace std;

int main()
{
    long ar[10] = {11, 3, 5, 9, 7, 4, 3, 5, 11, 3};
    cout << "The data: ";
    for (int i = 0; i < 10; ++i) {
        cout << ar[i] << " ";
    }
    cout << endl;
    cout << "After sort and unique: ";    
    int n = reduce(ar, 10);   
    for (int i = 0; i < n; ++i) {
        cout << ar[i] << " ";
    }
    cout << endl << endl;

    string str[10] = {"Bob", "Alex", "Candy", "Tony", "Zippo", "Candy", "Bob", "Jim", "Candy", "Zippo"};
    cout << "The string: ";
    for (int i = 0; i < 10; ++i) {
        cout << str[i] << " ";
    }
    cout << endl;
    cout << "After sort and unique: ";    
    int m = reduce(str, 10);   
    for (int i = 0; i < m; ++i) {
        cout << str[i] << " ";
    }
    cout << endl;       
    return 0;
}

template <class T>
int reduce(T str[], int n)
{
    sort(str, str + n);
    T* p = unique(str, str + n);
    return (int)(p - str);
}

6.

#include <iostream>  
#include <cstdlib>  
#include <ctime>  
#include <queue>

//定义顾客类 
class Customer
{
private:
    long arrive;
    int processtime;
public:
    Customer() { arrive = processtime = 0; }

    void set(long when)
    {
        processtime = std::rand() % 3 + 1;
        arrive = when;
    }   
    long when() const { return arrive; }
    int ptime() const { return processtime; }
};
typedef Customer Item;

//设置新顾客随机到来 
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));//随机初始化

    cout << "Case Study: Bank of Heather Automatic Teller\n";
    cout << "Enter maxmium size of queue: ";//最大的排队人数
    int qs;
    cin >> qs;
    std::queue <Item>line;//设有qs个人的队伍

    cout << "Enter the number of simulation hours: ";
    int hours;
    cin >> hours;
    long cyclelimit = MIN_PER_HR * hours;

    cout << "Enter the average number of customers per hours: ";
    double perhour;
    cin >> perhour;
    double min_per_cust;
    min_per_cust = MIN_PER_HR / perhour;//记录总的分钟数

//设置参数  
    Item temp;
    long turnaways = 0;
    long customers = 0;
    long served = 0;
    long sum_line = 0;
    int wait_time = 0;
    long line_wait = 0;

    for (int cycle = 0; cycle < cyclelimit; cycle++)
    {
        if (newcustomer(min_per_cust))
        {
            if (line.size()==qs)
                turnaways++;
            else
            {
                customers++;
                temp.set(cycle);
                line.push(temp);
            }
        }
        if (wait_time <= 0 && !line.empty())    
        {
            line.pop();//弹出，不需要item参数
            wait_time = temp.ptime();
            line_wait += cycle - temp.when();
            served++;           
        }                       
        if (wait_time > 0)
            wait_time--;
        sum_line += line.size(); 
    }

//报告结果 
    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";
    cout << "Done!\n";

    return 0;
}

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

7.

#include <iostream>
#include <vector>
#include <algorithm>
#include <ctime>

using namespace std;

vector<int> Lotto(int m, int n);
void show(int n) {cout << n << " ";}

int main()
{   
    srand((int)time(0));//用时间产生随机数种子  
    cout << "Diaplsy the random number:" << endl;
    vector<int> winner;
    winner = Lotto(51, 6);
    for_each(winner.begin(), winner.end(), show);

    return 0;
}

vector<int> Lotto(int m, int n)
{
    vector<int> temp;
    for (int i = 1; i <= m; i++)//创建矢量 
    {
        temp.push_back(i);//vector<int>输入 
    }
    random_shuffle(temp.begin(), temp.end());//随机排列 
    vector<int>::iterator last;
    last = (temp.begin(), temp.begin() + n);
    temp.erase(last, temp.end());//取前六位数字 
    //另外一种比较方便的方法：temp.resize(n);
    return temp;
}

8.

#include <iostream> 
#include <string>
#include <list>
#include <algorithm>

using namespace std;
void show(string & s);

int main()
{
    list<string> Mat;
    cout << "-----------Mat's friends-----------" << endl;
    cout << "Enter the name, and (quit to quit):" << endl;
    string temp1;
    getline(cin, temp1);
    while (temp1 != "quit")
    {
        Mat.push_back(temp1);
        cout << "Enter the name, and (quit to quit):" << endl;
        getline(cin, temp1);    
    }
    Mat.sort();
    cout << "Here are Mat's friends:" <<endl;
    for_each(Mat.begin(), Mat.end(), show);
    cout << endl;

    list<string> Pat;
    cout << "-----------Pat's friends-----------" << endl;
    cout << "Enter the name, and (quit to quit):" << endl;
    string temp2;
    getline(cin, temp2);
    while (temp2 != "quit")
    {
        Pat.push_back(temp2);
        cout << "Enter the name, and (quit to quit):" << endl;
        getline(cin, temp2);    
    }
    Pat.sort();
    cout << "Here are Pat's friends:" <<endl;
    for_each(Pat.begin(), Pat.end(), show);
    cout << endl;

    cout << "--------------friends--------------" << endl;  
    Mat.splice(Mat.end(), Pat);
    Mat.sort();
    Mat.unique();   
    cout << "All friends:" <<endl;
    for_each(Mat.begin(), Mat.end(), show);

    return 0;   
}

void show(string & s)
{
    cout << "friend'name："<< s << endl;
}

9.

#include <iostream>
#include <vector>
#include <list> 
#include <algorithm>
#include <ctime>

using namespace std;
const int num = 1000000;

int main()
{   
    vector<int> vi0;
    vector<int> vi;
    list<int> li;

    srand((int)time(0));//用时间产生随机数种子    
    for (int i = 0; i < num; i++)//初始化 
    {
        int temp = rand() * rand();
        vi0.push_back(temp);
        vi.push_back(temp);
        li.push_back(temp);
    }

    cout << "The time of sort() by STL: " << endl;
    clock_t start1 = clock();
    sort(vi.begin(), vi.end());
    clock_t end1 = clock();
    cout << (double)(end1 - start1) /CLOCKS_PER_SEC;
    cout << endl;

    cout << "The time of sort() by list: " << endl; 
    clock_t start2 = clock();   
    li.sort();
    clock_t end2 = clock();
    cout << (double)(end2 - start2) /CLOCKS_PER_SEC;
    cout << endl;   

    cout << "The time of sort() by copy: " << endl;
    copy(vi0.begin(), vi0.end(), li.begin());
    clock_t start3 = clock();   
    copy(li.begin(), li.end(), vi.begin()); 
    sort(vi.begin(), vi.end());
    copy(vi.begin(), vi.end(), li.begin());         
    clock_t end3 = clock();
    cout << (double)(end3 - start3) /CLOCKS_PER_SEC;
    cout << endl;   

    return 0;
}

10.

#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include<memory>

using namespace std;

struct Review {
    std::string title;
    int rating;
    double price;
};

bool operator<(const shared_ptr<Review> & r1, const shared_ptr<Review> & r2);
bool worseThan(const shared_ptr<Review> & r1, const shared_ptr<Review> & r2);
bool FillReview(Review & rr);
void ShowReview(const shared_ptr<Review> & rr);
void showmenu();
bool sorting1(const shared_ptr<Review> & r1, const shared_ptr<Review> & r2);

int main()
{
    vector <shared_ptr<Review>> books;
    Review temp;
    while (FillReview(temp)) {
        shared_ptr<Review> pd_temp(new Review(temp));
        books.push_back(pd_temp);
    }

    if (books.size() > 0)
    {
        cout<< "choose a way to show data.";
        int choice;
        showmenu();
        cin >> choice;
        while (choice <= 7 && choice > 0)
        {
            switch (choice)
            {
            case 1:
                for_each(books.begin(), books.end(), ShowReview);
                break;
            case 2:
                sort(books.begin(), books.end());
                for_each(books.begin(), books.end(), ShowReview);
                break;
            case 3:
                sort(books.begin(), books.end(), worseThan);
                for_each(books.begin(), books.end(), ShowReview);
                break;
            case 4:
                sort(books.begin(), books.end(), worseThan);
                reverse(books.begin(), books.end());
                for_each(books.begin(), books.end(), ShowReview);
                break;
            case 5:
                sort(books.begin(), books.end(), sorting1);
                for_each(books.begin(), books.end(), ShowReview);
                break;
            case 6:
                sort(books.begin(), books.end(), sorting1);
                reverse(books.begin(), books.end());
                for_each(books.begin(), books.end(), ShowReview);
                break;
            default:
                cout << "wrong number.";
                continue;
            }
            showmenu();
            cin >> choice;
        }
    }
    else
        cout << "No entries. ";
    cout << "Bye.\n";
    // cin.get();
    return 0;
}

bool operator<(const shared_ptr<Review> & r1, const shared_ptr<Review> & r2)
{
    if (r1->title < r2->title)
        return true;
    else if (r1->title == r2->title && r1->rating < r2->rating)
        return true;
    else
        return false;
}

bool worseThan(const shared_ptr<Review> & r1, const shared_ptr<Review> & r2)
{
    if (r1->rating < r2->rating)
        return true;
    else
        return false;
}

bool FillReview(Review & rr)
{
    std::cout << "Enter book title (quit to quit): ";
    getline(cin, rr.title);
    if (rr.title == "quit")
        return false;
    cout << "Enter book price:  ";
    cin >> rr.price;
    if (!cin)
        return false;

    std::cout << "Enter book rating: ";
    std::cin >> rr.rating;
    if (!cin)
        return false;
    // get rid of rest of input line
    while (std::cin.get() != '\n')
        continue;
    return true;
}

void ShowReview(const shared_ptr<Review> & rr)
{
    cout << "name\trating\tprice\n";
    cout << rr->title << "\t" << rr->rating << "\t" << rr->price << endl;
}

bool sorting1(const shared_ptr<Review> & r1, const shared_ptr<Review> & r2)
{
    if (r1->price < r2->price)
        return true;
    if (r1->price == r2->price && r1->rating < r2->rating)
        return true;
    else
        return false;
}

void showmenu()
{
    cout << "Please enter 1,2,3,4,5,6 or 7\n"
        << "1) by original order \t 2) by alphabet order  \n"
        << "3) by rating up      \t 4) by rating down     \n"
        << "5) by pricing up     \t 6) by pricing down    \n"  
        << "7) quit  \n";
}