【C++ Primer】【学习笔记】【第十章】关联容器之：set类型

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

插入方法

说明

set<string> set1;

set1.insert("the");

set1.insert("and");

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set对象中已存在，则保持set对象不变。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。

set<int> iset2;

iset2.insert(ivec.begin(), ivec.end());

ivec.begin()和ivec.end()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。返回值为void。

三、set对象获取元素

查询方法

说明

iset2.count(k)

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容器存储的键必须唯一。

iset2.find(k)

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。

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。

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 wordvoid 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 wordvoid 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.outEnter filename:nameEnter text2(Ctrl + D or Ctrl + Z to end):yj zs ls ww zlword            timesyj              1zl              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): classnon-plural version: classEnter a word(Ctrl + D or Ctrl + Z): successnon-plural version: successEnter a word(Ctrl + D or Ctrl + Z): bikesnon-plural version: bikeEnter a word(Ctrl + D or Ctrl + Z): tables    non-plural version: tableEnter 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 jklWould you like to read a book?(Yes/No): yYou can read this book: defDid you read it?(Yes/No): yTime over?(Yes/No): nWould you like to read a book?(Yes/No): yYou can read this book: jklDid you read it?(Yes/No): yTime over?(Yes/No): yBooks read: defjklBook not read: abcghi