【C++ Primer】【学习笔记】【第十章】关联容器之：set类型

川长思鸟来 2022-08-06 16:23 153阅读 0赞

**一、set容器定义**

set容器支持大部分的map操作，但如下两种操作除外：

1、set不支持下标操作；

2、set没有定义mapped\_type类型。

注：set存储的元素仅仅是键，而不存储所关联的值。与map一样，set容器存储的键也必须唯一，而且不能修改。

**二、set对象插入元素**

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      插入方法 
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      说明 
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      set&lt;string&gt; set1; 
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      set1.insert("the"); 
    </div> 
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      set1.insert("and"); 
    </div> </td> 
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      如果键不在set对象中，则插入一个该键的新元素；如果该键在 
     <span style="font-family:微软雅黑; font-size:14px">set对象</span>中已存在，则保持set 
     <span style="font-family:微软雅黑; font-size:14px">对象</span>不变。 
     <span style="background-color:inherit">该函数返回一个pair类型的对象，包含一个指向该键元素的set迭代器，以及一个bool类型的对象，表示是否插入了该元素。</span> 
    </div> </td> 
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      set&lt;int&gt; iset2; 
    </div> 
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      iset2.insert(ivec.begin(), ivec.end()); 
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     <span style="font-family:微软雅黑; font-size:14px">ivec.begin()</span>和 
     <span style="font-family:微软雅黑; font-size:14px">ivec.end()</span>是标记元素范围的迭代器。对于这些元素，如果其键在set对象中不存在，则将该键对应的元素插入m。 
     <span style="background-color:inherit">返回值为void。</span> 
    </div> </td> 
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**三、set对象获取元素**

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      查询方法 
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      说明 
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      iset2.count(k) 
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      返回set容器中k的出现次数。返回值只能是0或者1，因为set容器 
     <span style="font-family:微软雅黑; font-size:14px; line-height:1.5">存储的键必须唯一</span>。 
    </div> </td> 
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      iset2.find(k) 
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      如果set容器中存在按k索引的元素，则返回指向该元素的迭代器。如果不存在，则返回超出末端迭代器。 
    </div> 
    <div style="min-width:2px; background-color:inherit">
      注：使用返回的迭代器，只能对值进行读取，而不能进行修改。因为set容器中的键是const类型的。 
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</table>

**习题10.23：单词统计，排除黑名单中的词**

#include <iostream>
    #include <fstream>
    #include <string>
    #include <utility>
    #include <vector>
    #include <map>
    #include <set>
    using namespace std;
    
    // using set to store removed word
    void restricted_wc_v1(ifstream &remove_file, map<string, int> &word_count)
    {
        set<string> excluded;
        string remove_word;
        while (remove_file >> remove_word)
        {
            excluded.insert(remove_word);
        }
    
        cout << "Enter text1(Ctrl + D or Ctrl + Z to end): " << endl;
        string word;
        while (cin >> word)
        {
            if (!excluded.count(word))
            {
                ++word_count[word];
            }
        }
    
        return;
    }
    
    // using vector to store removed word
    void restricted_wc_v2(ifstream &remove_file, map<string, int> &word_count)
    {
        vector<string> excluded;
        string remove_word;
        while (remove_file >> remove_word)
        {
            excluded.push_back(remove_word);
        }
    
        cout << "Enter text2(Ctrl + D or Ctrl + Z to end): " << endl;
        string word;
        while (cin >> word)
        {
            bool find = false;
    
            vector<string>::iterator iter = excluded.begin();
            while (iter != excluded.end())
            {
                if (word == *iter)
                {
                    find = true;
                    break;
                }
                iter++;
            }
           
            if (!find)
            {
                ++word_count[word];
            }
        }
    
        return;
    }
    
    int main()
    {
        map<string, int> word_count;
        string filename;
    
        cout << "Enter filename: " << endl;
        cin >> filename;
        ifstream filestream(filename.c_str());
        if (!filestream)
        {
            cout << "Error: open file fail!" << endl;
            return -1;
        }
    
        restricted_wc_v2(filestream, word_count);
    
        cout << "word\t\t" << "times" << endl;
        map<string, int>::iterator iter = word_count.begin();
        while (iter != word_count.end())
        {
            cout << iter->first << "\t\t" << iter->second << endl;
            iter++;
        }
    
        return 0;
    }

[chapter10]$ ./a.out
    Enter filename:
    name
    Enter text2(Ctrl + D or Ctrl + Z to end):
    yj zs ls ww zl
    word            times
    yj              1
    zl              1

**习题10.24：单词从复数转换成单数**

#include <iostream>
    #include <fstream>
    #include <string>
    #include <utility>
    #include <vector>
    #include <map>
    #include <set>
    using namespace std;
    
    int main()
    {
        set<string> excluded;
    
        // setup excluded
        excluded.insert("class");
        excluded.insert("success");
        // new word add here...
    
        string word;
        cout << "Enter a word(Ctrl + D or Ctrl + Z): " << endl;
        while (cin >> word)
        {
            if (!excluded.count(word))
            {
                word.resize(word.size() - 1);
            }
    
            cout << "non-plural version: " << word << endl;
            cout << "Enter a word(Ctrl + D or Ctrl + Z): " << endl;
        }
    
        return 0;
    }

[chapter10]$ ./a.out 
    Enter a word(Ctrl + D or Ctrl + Z): 
    class
    non-plural version: class
    Enter a word(Ctrl + D or Ctrl + Z): 
    success
    non-plural version: success
    Enter a word(Ctrl + D or Ctrl + Z): 
    bikes
    non-plural version: bike
    Enter a word(Ctrl + D or Ctrl + Z): 
    tables    
    non-plural version: table
    Enter a word(Ctrl + D or Ctrl + Z):

**习题10.25：读书列表管理**

#include <iostream>
    #include <fstream>
    #include <string>
    #include <utility>
    #include <vector>
    #include <map>
    #include <set>
    #include <ctime>
    using namespace std;
    
    int main()
    {
        vector<string> books;
        set<string> readedBooks;
        string name;
    
        // establish books to read
        cout << "Enter names for books you'd like to read.(Ctrl + D or Ctrl + Z to end): " << endl;
        while (cin >> name)
        {
            books.push_back(name);
        }
        cin.clear();
    
        bool timeOver = false;
        string answer, bookName;
        srand((unsigned)time(NULL));
    
        while (!timeOver & !books.empty())
        {
            cout << "Would you like to read a book?(Yes/No): " << endl;
            cin >> answer;
    
            if ('y' == answer[0] || 'Y' == answer[0])
            {
                int i = rand() % books.size();
                bookName = books[i];
                cout << "You can read this book: " << bookName << endl;
                readedBooks.insert(bookName);
                books.erase(books.begin() + i);
                
                cout << "Did you read it?(Yes/No): " << endl;
                cin >> answer;
                if ('n' == answer[0] || 'N' == answer[0])
                {
                    readedBooks.erase(bookName);
                    books.push_back(bookName);
                }
            }
    
            cout << "Time over?(Yes/No): " << endl;
            cin >> answer;
            if ('y' == answer[0] || 'Y' == answer[0])
            {
                timeOver = true;
            }
        }
    
        if (timeOver)
        {
            cout << "Books read: " << endl;
            for (set<string>::iterator sit = readedBooks.begin(); sit != readedBooks.end(); ++sit)
            {
                cout << *sit << endl;
            }
    
            cout << "Book not read: " << endl;
            for (vector<string>::iterator vit = books.begin(); vit != books.end(); ++vit)
            {
                cout << *vit << endl;
            }
        }
        else
        {
            cout << "Congratulatios! You've read all these books!" << endl;
        }
    
        return 0;
    }

[chapter10]$ ./a.out 
    Enter names for books you'd like to read.(Ctrl + D or Ctrl + Z to end): 
    abc def ghi jkl
    Would you like to read a book?(Yes/No): 
    y
    You can read this book: def
    Did you read it?(Yes/No): 
    y
    Time over?(Yes/No): 
    n
    Would you like to read a book?(Yes/No): 
    y
    You can read this book: jkl
    Did you read it?(Yes/No): 
    y
    Time over?(Yes/No): 
    y
    Books read: 
    def
    jkl
    Book not read: 
    abc
    ghi