C++ Primer Plus 学习笔记第十六章泛型编程 STL模板类

以你之姓@ 2022-01-14 10:37 216阅读 0赞

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先说第一个容器

![20190614113450681.png][]

vector: 就是第四章说的那货。好像没啥可说的

大概用法格式

![20190614113459497.png][]

程序示例

#include <iostream>
    #include <string>
    #include <vector>
    
    const int NUM = 5;
    int main()
    {
      using std::vector;
      using std::string;
      using std::cin;
      using std::endl;
      using std::cout;
    
      vector<int> ratings(NUM);
      vector<string> titles(NUM);
      cout << "You will do exactly as told. You will enter\n"
           << NUM << " book titles and your ratings (0-10).\n";
      int i;
      for ( i=0; i < NUM; i++)
      {
        cout << "Enter title #" << i + 1 << ": ";
        getline(cin, titles[i]);
        cout << "Enter your rating (0-10): ";
        cin >> ratings[i];
        cin >> ratings[i];
        cin.get();
      }
      cout << "Thank you. You entered the following:\n"
           << "Rating\tBook\n";
      for(i = 0; i < NUM; i++)
      {
        cout << ratings[i] << "\t" << titles[i] << endl;
      }
    
      return 0;
    }

vector的可用函数

![2019061411392149.png][]

迭代器

其实就是广义指针 可以指向指针或类似指针操作的对象 嗯。。 这个解释可以有

定义和基本用法

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其他用法

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模板追加

push\_back()类似appends()

指定区间删除

erase() 距离

scores.earse(scores.begin(), scores.begin() + 2); 删除scores的第一个和第二个元素

插入

insert()

![20190617151939614.png][]

![20190617151950824.png][]

将后面两个元素的内容 插到old\_v的前面。。 卧槽 还有这样操作的

以上方法程序示例

#include <iostream>
    #include <string>
    #include <vector>
    
    struct Review {
      std::string title;
      int rating;
    };
    bool FillReview(Review & rr);
    void ShowReview(const Review & rr);
    
    int main()
    {
      using std::cout;
      using std::vector;
    // Review类型模板类 books
      vector<Review> books;
      Review temp;
      while (FillReview(temp))
    // 追加元素
        books.push_back(temp);
    // 返回元素长度
      int num = books.size();
      if (num > 0)
      {
        cout << "Thank you. You entered the following:\n"
             << "Rating\tBook\n";
        for (int i = 0; i < num; i++)
          ShowReview(books[i]);
        cout << "Reprising:\n"
             << "Rating\tBook\n";
    // Review类型的迭代器
        vector<Review>::iterator pr;
    // 通过迭代器来显示元素内容
        for (pr = books.begin(); pr != books.end(); pr++)
          ShowReview(*pr);
    // 复制构造函数
        vector <Review> oldlist(books);
        if (num > 3)
        {
    // 删除指定区间元素
          books.erase(books.begin() + 1, books.begin() + 3);
          cout << "After erasure:\n";
          for (pr = books.begin(); pr != books.end(); pr++)
            ShowReview(*pr);
    // 将指定区间的元素集插入到books的前面
          books.insert(books.begin(), oldlist.begin() + 1, oldlist.begin() + 2);
          cout << "After insertion:\n";
          for (pr = books.begin(); pr != books.end(); pr++)
            ShowReview(*pr);
        }
    // 交换两个vector内容
        books.swap(oldlist);
        cout << "Swapping oldlist with books:\n";
        for (pr = books.begin(); pr != books.end(); pr++)
          ShowReview(*pr);
      }
      else
        cout << "Nothing entered, nothing gained.\n";
      return 0;
    }
    
    bool FillReview(Review & rr)
    {
      std::cout << "Enter book title (quit to quit): ";
      std::getline(std::cin, rr.title);
      if (rr.title == "quit")
        return false;
      std::cout << "Enter book rating: ";
      std::cin >> rr.rating;
      if (!std::cin)
        return false;
      while (std::cin.get() != '\n')
        continue;
      return true;
    }
    
    void ShowReview(const Review & rr)
    {
      std::cout << rr.rating << "\t" << rr.title << std::endl;
    }

程序示例

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其他STL函数

for\_each()

接收3个参数。 第一个，第二个参数表示的是容器区间，第三个表示要操作的函数（就是把第一个到第二个参数的区间的对象逐一传递到第三个参数，当做该函数的参数传递进去）

![20190617161232625.png][]

Random\_shuffle()

该函数接收两个参数，作为指定区间。然后随机排列他们

![20190617161616516.png][]

sort()

排序

两个版本

第一个版本 如果是C++的内置类型（或者是标准函数库中的类型 有定义operator<()的）或者自定义了operator<()函数

sort(book.begin(), books.end()) 默认进行升序排列（要求容器支持随机访问）

第二个版本 不是C++的内置类型，或者不想按照升序排列

sort()接收三个参数。第一、二个与前面一样，就是第三个是比较函数。sort()会将每个元素都放到该函数中进行比较。返回true或false

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![20190617162926405.png][]

程序代码示例

#include <iostream>
    #include <string>
    #include <vector>
    #include <algorithm>
    
    struct Review{
      std::string title;
      int rating;
    };
    
    bool operator< (const Review & r1, const Review & r2);
    bool worseThan(const Review & r1, const Review & r2);
    bool FillReview(Review & rr);
    void ShowReview(const Review & rr);
    
    int main()
    {
      using namespace std;
    
      vector<Review> books;
      Review temp;
      while (FillReview(temp))
        books.push_back(temp);
      if (books.size() > 0)
      {
        cout << "Thank you. You entered the following "
             << books.size() << " ratings:\n"
             << "Rating\tBook\n";
    // 通过ShowReview迭代输出books.begin()到books.end()(不包括end)的元素
        for_each(books.begin(), books.end(), ShowReview);
    
    // 升序
        sort(books.begin(), books.end());
        cout << "Sorted by title:\nRating\tBook\n";
        for_each(books.begin(), books.end(), ShowReview);
    
    // 将books所有元素丢到worseThan中排序
        sort(books.begin(), books.end(), worseThan);
        cout <<"Sorted by rating:\nRating\tBook\n";
        for_each(books.begin(), books.end(), ShowReview);
    
    // 随机
        random_shuffle(books.begin(), books.end());
        cout << "After shuffling:\nRating\tBook\n";
        for_each(books.begin(), books.end(), ShowReview);
      }
      else
        cout << "No entries. ";
      cout << "Bye.\n";
      return 0;
    }
    
    bool operator<(const Review & r1, const 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 Review & r1, const Review & r2)
    {
      if (r1.rating < r2.rating)
        return true;
      else
        return false;
    }
    
    bool FillReview(Review & rr)
    {
      std::cout << "Enter book title (quit to quit): ";
      std::getline(std::cin, rr.title);
      if (rr.title == "quit")
        return false;
      std::cout << "Enter book rating: ";
      std::cin >> rr.rating;
      if (!std::cin)
        return false;
      while(std::cin.get() != '\n')
        continue;
      return true;
    }
    
    void ShowReview(const Review & rr)
    {
      std::cout << rr.rating << "\t" << rr.title << std::endl;
    }

程序执行结果

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C++ 的for循环

以前说的for循环

for (double x : prices)
        cout << x << std::endl;

容器也可以用这个 类似于for\_each()

for (auto x : books) ShowReview(x);

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完结

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