C++ 标准模板库STL set 使用方法与应用介绍（一）

本文主要介绍C++标准模板库STL中set和multiset的使用方法，包括容器类的基本构造、常用方法及集合操作，帮助理解其在编程中的应用。

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这次先看例子程序：

#include <iostream>
#include <set>
#include <algorithm>
#include <iterator>
using namespace std;

int main()
{
    /* type of the collection:
     * - no duplicates
     * - elements are integral values
     * - descending order
     */
    typedef set<int,greater<int> > IntSet;

    IntSet coll1;        // empty set container

    // insert elements in random order
    coll1.insert(4);
    coll1.insert(3);
    coll1.insert(5);
    coll1.insert(1);
    coll1.insert(6);
    coll1.insert(2);
    coll1.insert(5);

    cout<<"typedef set<int,greater<int> > IntSet  由大到小："<<endl;
    // iterate over all elements and print them
    IntSet::iterator pos;
    for (pos = coll1.begin(); pos != coll1.end(); ++pos)
    {
        cout << *pos << ' ';
    }
    cout << endl;

    // insert 4 again and process return value
    pair<IntSet::iterator,bool> status = coll1.insert(4);
    if (status.second)
    {
        cout << "4 inserted as element "
             << distance(coll1.begin(),status.first) + 1
             << endl;
    }
    else
    {
        cout << "4 already exists" << endl;
    }
    status = coll1.insert(512);
    if (status.second)
    {
        cout << "512 inserted as element "
             << distance(coll1.begin(),status.first) + 1
             << endl;
    }
    else
    {
        cout << "512 already exists" << endl;
    }
    // print all elements of the copy
    cout<<"after pair<IntSet::iterator,bool> status = coll1.insert(4 and 512):"<<endl;
    copy (coll1.begin(), coll1.end(),ostream_iterator<int>(cout," "));
    cout<<endl;
    // assign elements to another set with ascending order
    set<int> coll2(coll1.begin(),coll1.end());
    cout<<"after set<int> coll2(coll1.begin(),coll1.end()) coll2: 由小到大："<<endl;
    // print all elements of the copy
    copy (coll2.begin(), coll2.end(),ostream_iterator<int>(cout," "));
    cout << endl;

    // remove all elements up to element with value 3
    coll2.erase (coll2.begin(), coll2.find(3));

    cout<<"after coll2.erase (coll2.begin(), coll2.find(3)) :"<<endl;
    // print all elements
    copy (coll2.begin(), coll2.end(),ostream_iterator<int>(cout," "));

    // remove all elements with value 5
    int num;
    num = coll2.erase (5);
    cout<<"after ：num = coll2.erase (5) :"<<endl;
    cout <<endl<< num << " element(s) removed" << endl;

    // print all elements
    copy (coll2.begin(), coll2.end(),ostream_iterator<int>(cout," "));
    cout << endl;
}
/*******************
程序运行结果如下：
typedef set<int,greater<int> > IntSet  由大到小：
6 5 4 3 2 1
4 already exists
512 inserted as element 1
after pair<IntSet::iterator,bool> status = coll1.insert(4 and 512):
512 6 5 4 3 2 1
after set<int> coll2(coll1.begin(),coll1.end()) coll2: 由小到大：
1 2 3 4 5 6 512
after coll2.erase (coll2.begin(), coll2.find(3)) :
3 4 5 6 512 after ：num = coll2.erase (5) :

1 element(s) removed
3 4 6 512

Process returned 0 (0x0)   execution time : 0.496 s
Press any key to continue.

********************/