C++ Primer Plus 第六版第十六章课后编程练习答案

深藏阁楼爱情的钟 2023-07-25 14:25 15阅读 0赞

play.cpp

#include <iostream>
    using namespace std;
    #include <string>
    
    bool IsHui(const string &str);
    
    int main()
    {
        cout << "Enter input(empty input to quit): ";
        string input;
        getline(cin, input);
        while (cin && input.size()>0)
        {
            if(IsHui(input))
                cout << "Yes.\n";
            else
                cout << "No.\n";
            cout << "Enter input(empty input to quit): ";
            getline(cin, input);
        }
        cout << "End.\n";
    
        return 0;
    }
    
    bool IsHui(const string &str)
    {
        string f(str.rbegin(), str.rend());//字符串反转
        return (str == f);
    }

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本题要求在考虑空格、大小写和标点符号的情况下来测试回文，整体程序框架可以与上一题完全一样，只需要修改判断是否是回文的bool函数。

在判断是否是回文之前，我们必须把空格和标点符号去掉，然后把大小写归一化才行。对于去掉空格和标点符号，最简单的方法是调用cctype库中的erase()函数，该函数会删去指定的字符，那么我们可以使用isalpha()函数来判断是否是字母，如果不是字母，即空格或者各式各样的标点符号，则调用erase()函数将其删去。对于大小写的归一化，我们可以统一到一种格式上，比如按照题目中举的例子，就是统一都格式化成小写，那么就是使用tolower()函数。

#include <iostream>
    using namespace std;
    #include <string>
    #include <cctype>
    
    bool IsHui(const string &str);
    
    int main()
    {
        cout << "Enter input(empty input to quit): ";
        string input;
        getline(cin, input);
        while (cin && input.size()>0)
        {
            if(IsHui(input))
                cout << "Yes.\n";
            else
                cout << "No.\n";
            cout << "Enter input(empty input to quit): ";
            getline(cin, input);
        }
        cout << "End.\n";
    
        return 0;
    }
    
    bool IsHui(const string &str)
    {
        string str_test = str;//必须有
        for(auto i = str_test.begin(); i != str_test.end();) //i是str_test各元素所在的位置,*i是元素
        {
            if(!isalpha(*i))
            {
                i = str_test.erase(i);//该位置的元素去掉
                continue;
            }
            else
            {
                *i = tolower(*i);
                i++;
            }
        }
        string f(str_test.rbegin(), str_test.rend());
        return (str_test == f);
    }

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play.cpp

//改自清单16.3
    #include <iostream>
    using namespace std;
    #include <cctype>
    #include <cstdlib>
    #include <ctime>
    #include <string>
    #include <vector>
    #include <fstream>
    
    int main()
    {
        const string filename = "wordlist.txt";
        vector<string> wordlist;
        ifstream fin;
        fin.open(filename.c_str());
        if(fin.is_open() == false)
        {
            cerr << "Can't open file.Bye.\n";
            exit(EXIT_FAILURE);
        }
        string temp;
        while (fin >> temp)
            wordlist.push_back(temp);
    
    //以下按清单16.3
        const int NUM = wordlist.size();
        srand(time(0));
        char play;
        cout << "Will you play a word game? <y/n>";
        cin >> play;
        play = tolower(play);
        while (play == 'y')
        {
            string target = wordlist[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\n"
            << "one 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 guessed 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 word is " << target << ".\n";
            cout << "Will you play another? <y/n>";
            cin >> play;
            play = tolower(play);
        }
        cout << "Bye\n";
    
        return 0;
    }

play.cpp

//排序，去重
    #include <iostream>
    using namespace std;
    #include <algorithm>
    
    int reduce(long ar[], int n);
    
    int main()
    {
        long arr_test[10] = {156, 124, 23, 43, 35, 23, 124, 199, 210, 56};
        cout << "Original array:\n";
        for(int i = 0; i < 10; i++)
            cout << arr_test[i] << " ";
        cout << endl;
    
        int newsize = reduce(arr_test, 10);//返回缩减后数组中的元素数目
        cout << "Newsize: " << newsize << endl;
        cout << "After reduction, array:\n";
        for(int i = 0; i < newsize; i++)
            cout << arr_test[i] << " ";
        cout << endl;
    
        return 0;
    }
    
    int reduce(long ar[], int n)
    {
        sort(ar, ar + n);//排序
        long * arr_new;
        arr_new = unique(ar, ar + n);//去重
        //用unique()函数返回结果区间结尾的特点，将该结尾指针地址赋给一个long指针，将该地址减去实参的数组名地址，即是缩减后的元素数目
        return arr_new - ar;
    }

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本题是编写练习4的延伸，要求我们把原本的long数组修改为模板类，然后分别使用long实例和string实例来验证。

我们依然沿用编程练习4的思路和程序框架，首先把reduce()函数的实参进行修改，ar\[\]现在不再是long数组了，而是模板类T的数组，那么对应的在函数内部声明的new\_ar指针的类型也就相应变成T模板类。

play.cpp

//改自第4题
    #include <iostream>
    using namespace std;
    #include <algorithm>
    
    template <class T>
    int reduce(T ar[], int n);
    
    int main()
    {
        long arr_test[10] = {156, 124, 23, 43, 35, 23, 124, 199, 210, 56};
        cout << "Original array:\n";
        for(int i = 0; i < 10; i++)
            cout << arr_test[i] << " ";
        cout << endl;
        int newsize = reduce(arr_test, 10);//返回缩减后数组中的元素数目
        cout << "Newsize: " << newsize << endl;
        cout << "After reduction, the long array:\n";
        for(int i = 0; i < newsize; i++)
            cout << arr_test[i] << " ";
        cout << endl;
    
        cout << "The second test array: \n";
        string arr_test2[10] = {"hah", "china", "play", "end", "hah", "play", "speak", "play", "zero", "apple"};
        cout << "Original array:\n";
        for(int i = 0; i < 10; i++)
            cout << arr_test2[i] << " ";
        cout << endl;
        int newsize2 = reduce(arr_test2, 10);//返回缩减后数组中的元素数目
        cout << "Newsize: " << newsize2 << endl;
        cout << "After reduction, the long array:\n";
        for(int i = 0; i < newsize2; i++)
            cout << arr_test2[i] << " ";
        cout << endl;
    
        return 0;
    }
    
    template <class T>
    int reduce(T ar[], int n)
    {
        sort(ar, ar + n);//排序
        T * arr_new;
        arr_new = unique(ar, ar + n);//去重
        //用unique()函数返回结果区间结尾的特点，将该结尾指针地址赋给一个long指针，将该地址减去实参的数组名地址，即是缩减后的元素数目
        return arr_new - ar;
    }

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本题要求我们对程序清单12.12进行修改，使用STL queue模板类来代替Queue类。我们可以沿用程序清单12.12的程序框架，把"queue.h"换成<queue>即可。同时将queue.h内声明的Customer类放在同一个文件中声明和定义，放弃Queue类，转而使用queue<Customer>模板类来代替。

所以我们只需要把main()函数里面的Queue类声明改为queue<Customer>类声明即可.

play.cpp

//改自清单12.12
    #include <iostream>
    using namespace std;
    #include <queue>
    #include <cstdlib>
    #include <ctime>
    
    class Customer
    {
        long arrive;
        int processtime;
    public:
        Customer() {arrive = processtime = 0;}
        void set(long when) {processtime = rand()%3 + 1; arrive = when;}
        long when() const { return arrive;}
        int ptime() const { return processtime;}
    };
    
    
    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: ";
        int qs;
        cin >> qs;
        queue<Customer> line;
    
        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 hour: ";
        double perhour;
        cin >> perhour;
        double min_per_cust;
        min_per_cust = MIN_PER_HR / perhour;
    
        Customer 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(qs == line.size())
                    turnaways++;
                else
                {
                    customers++;
                    temp.set(cycle);
                    line.push(temp);
                }
            }
            if(wait_time <= 0 && !line.empty())
            {
                temp = line.front();
                wait_time = temp.ptime();
                line_wait += cycle - temp.when();
                served++;
                line.pop();
            }
            if(wait_time > 0)
                wait_time--;
            sum_line += line.size();
        }
    
        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 (rand() * x / RAND_MAX < 1);
    }

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play.cpp

#include <iostream>
    using namespace std;
    #include <vector>
    #include <algorithm>
    vector<int> Lotto(int cnum, int rnum);
    
    int main()
    {
        vector<int> winners;
        winners = Lotto(51, 6);
        cout << "Winner's number:\n";
        for(auto i = winners.begin(); i != winners.end(); i++)
            cout << *i << " ";
        cout << endl;
    
        return 0;
    }
    
    vector<int> Lotto(int cnum, int rnum)
    {
        vector<int> ticket(cnum);
        for(int i = 0; i < cnum; i++)
            ticket[i] = i + 1;
        random_shuffle(ticket.begin(), ticket.end());
        vector<int> choose(rnum);
        for(int i = 0; i < rnum; i++)
            choose[i] = ticket[i];
        sort(choose.begin(), choose.end());
    
        return choose;
    }

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play.cpp

#include <iostream>
    using namespace std;
    #include <vector>
    #include <string>
    #include <algorithm>
    
    int main()
    {
        vector<string> mat_f, pat_f, total_f;//3个容器
        cout << "Enter Mat's friends(empty line to quit):\n";
        string temp;
        while (getline(cin, temp))
        {
            mat_f.push_back(temp);
            total_f.push_back(temp);
            if(temp[0] == '\0')
                break;
        }
        cout << "The following are Mat's friends:\n";
        sort(mat_f.begin(), mat_f.end());
        for(auto i = mat_f.begin(); i != mat_f.end(); i++)
            cout << *i << endl;
        cout << endl << endl;
    
        cout << "Enter Pat's friends(empty line to quit):\n";
        while (getline(cin, temp))
        {
            pat_f.push_back(temp);
            total_f.push_back(temp);
            if(temp[0] == '\0')
                break;
        }
        cout << "The following are Pat's friends:\n";
        sort(pat_f.begin(), pat_f.end());
        for(auto i = pat_f.begin(); i != pat_f.end(); i++)
            cout << *i << endl;
        cout << endl << endl;
    
        sort(total_f.begin(), total_f.end());
        unique(total_f.begin(), total_f.end());
        cout << "There are " << total_f.size() << " friends to be invited in total:\n";
        for(auto i = total_f.begin(); i != total_f.end(); i++)
            cout << *i << endl;
        cout << endl << endl;
    
        return 0;
    }

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play.cpp

#include <iostream>
    using namespace std;
    #include <algorithm>
    #include <ctime>
    #include <vector>
    #include <list>
    #include <string>
    
    const int NUM = 10000000;
    int main()
    {
        cout << "-------begin--------" << endl;
        srand(time(0));
        vector<int> vi0(NUM);
        for(int i = 0; i < NUM; i++)
            vi0[i] = rand();
    
        vector<int> vi(vi0);//创建vector<int>对象vi和list<int>对象li，它们的长度都和初始值与vi0相同
        list<int> li(vi0.begin(), vi0.end());
        cout << "Measure the sort() algorithm's running time for vector<int>:\n";
        clock_t vector_start = clock();
        sort(vi.begin(), vi.end());
        clock_t vector_end = clock();
        cout << "The time is " << (double)(vector_end - vector_start) / CLOCKS_PER_SEC << "s.\n";
    
        cout << "Measure the sort() algorithm's running time for list<int>:\n";
        clock_t list_start = clock();
        li.sort();
        clock_t list_end = clock();
        cout << "The time is " << (double)(list_end - list_start) / CLOCKS_PER_SEC << "s.\n";
    
        cout << "Measure the copy() and sort() algorithm's running time:\n";
        copy(vi0.begin(), vi0.end(), li.begin());//li重置为排序的vi0的内容
        clock_t copy_start = clock();
        copy(li.begin(), li.end(), vi.begin());//将li的内容复制到vi中
        sort(vi.begin(), vi.end());//对vi进行排序
        copy(vi.begin(), vi.end(), li.begin());//并将结果复制到li中
        clock_t copy_end = clock();
        cout << "The time is " << (double)(copy_end - copy_start) / CLOCKS_PER_SEC << "s.\n";
    
        return 0;
    }

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10.

play.cpp

//改自清单16.9
    #include <iostream>
    using namespace std;
    #include <algorithm>
    #include <vector>
    #include <string>
    
    struct Review
    {
        string title;
        int rating;
        double price;
    };
    
    //按题，不使用vector<Review>来存储输入，而使用vector<shared_ptr<Review>>
    bool operator <(const shared_ptr<Review> &r1, const shared_ptr<Review> &r2);
    //添加betterthan(),expensivethan(),cheapthan()函数，来让用户选择按评级降序显示，按价格降序显示，按价格升序显示
    bool worsethan(const shared_ptr<Review> &r1, const shared_ptr<Review> &r2);
    bool betterthan(const shared_ptr<Review> &r1, const shared_ptr<Review> &r2);
    bool expensivethan(const shared_ptr<Review> &r1, const shared_ptr<Review> &r2);
    bool cheapthan(const shared_ptr<Review> &r1, const shared_ptr<Review> &r2);
    bool FillReview(Review &rr);
    void ShowReview(const shared_ptr<Review> &rr);
    
    int main()
    {
        vector<shared_ptr<Review>> books;
        Review temp;
        while (FillReview(temp))
        {
            shared_ptr<Review> newtemp(new Review(temp));
            books.push_back(newtemp);
        }
        if(books.size() > 0)
        {
            cout << "Thank you. You entered the following "
            << books.size() << " ratings:\n"
            << "Rating\tBook\n";
            for_each(books.begin(), books.end(), ShowReview);
    
            cout << "Please choose a type to show(0 for original order, 1 for alphabet order, 2 for rating ascend order, \n3 for rating discend order, 4 for price ascend order, 5 for price discend order, q for quit): ";
            int input;
            while (cin >> input)
            {
                switch (input)
                {
                    case 0:
                        break;
                    case 1:
                        sort(books.begin(), books.end());
                        break;
                    case 2:
                        sort(books.begin(), books.end(), worsethan);
                        break;
                    case 3:
                        sort(books.begin(), books.end(), betterthan);
                        break;
                    case 4:
                        sort(books.begin(), books.end(), cheapthan);
                        break;
                    case 5:
                        sort(books.begin(), books.end(), expensivethan);
                        break;
                    default:
                        break;
                }
                for_each(books.begin(), books.end(), ShowReview);
                cout << "Please choose a type to show(0 for original order, 1 for alphabet order, 2 for rating ascend order, \n3 for rating discend order, 4 for price ascend order, 5 for price discend order, q for quit): ";
            }
    
        }
        else
            cout << "No entries. ";
        cout << "Bye.\n";
    
        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 betterthan(const shared_ptr<Review> &r1, const shared_ptr<Review> &r2)
    {
        if(r1->rating > r2->rating)
            return true;
        else
            return false;
    }
    
    bool expensivethan(const shared_ptr<Review> &r1, const shared_ptr<Review> &r2)
    {
        if(r1->price > r2->price)
            return true;
        else
            return false;
    }
    
    bool cheapthan(const shared_ptr<Review> &r1, const shared_ptr<Review> &r2)
    {
        if(r1->price < r2->price)
            return true;
        else
            return false;
    }
    
    bool FillReview(Review & rr)
    {
        cout << "Enter book title(q to quit): ";
        getline(cin, rr.title);
        if(rr.title == "q")
            return false;
        cout << "Enter book rating: ";
        cin >> rr.rating;
        cout << "Enter book price: ";
        cin >> rr.price;
        if(!cin)
            return false;
        while (cin.get() != '\n')
            continue;
        return true;
    }
    
    void ShowReview(const shared_ptr<Review> &rr)
    {
        cout << rr->rating << "\t" << rr->price << "\t" << rr->title << endl;
    }

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