C++范型程序补充阅读

(1)下面程序通过输入流迭代器来填充vector容器，通过输出流迭代器来写入“流cout”。程序执行时，如果输入为：1 2 3 4 5 q
则输出为：1,2,3,4,5,
1 | 2 | 3 | 4 | 5 |
请填空将程序补充完整。

#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
int main()
{
   vector<int> col1;
   istream_iterator<int> intreader(cin),eof;;
   while(intreader!=eof)
   {
      col1.push_back(_______________);          // （1）
      _______________;                        // （2）
   }
   _______________ intwriter(cout,",");   // （3）
   copy(col1.begin(),col1.end(),intwriter);
   cout<<endl;
   copy(col1.begin(),col1.end(),_______________);   // （4）
   cout<<endl;
   return 0;
}

参考解答：
（1）*intreader 　（2）++intreader
（3）ostream_iterator （4）ostream_iterator(cout,” | “)
等价程序：

#include<iostream>
#include<vector>
#include<algorithm>
#include<iterator>
using namespace std;
int main()
{
   vector<int> col1(5);
   copy(istream_iterator<int>(cin),istream_iterator<int>(),col1.begin());
   ostream_iterator<int> intwriter(cout,",");
   copy(col1.begin(),col1.end(),intwriter);
   cout<<endl;
   copy(col1.begin(),col1.end(),ostream_iterator<int>(cout,"|"));
   cout<<endl;
   return 0;
}

(2)set用法

#include <algorithm>
#include<set>
#include<iterator>
#include<iostream>
using namespace std;
int main()
{
    set<int>eg1;
//插入
    eg1.insert(1);
    eg1.insert(100);
    eg1.insert(5);
    eg1.insert(1);//元素1因为已经存在所以set中不会再次插入1
    eg1.insert(10);
    eg1.insert(9);
//遍历set，可以发现元素是有序的
    set<int>::iterator set_iter=eg1.begin();
    cout<<"Set named eg1:"<<endl;
    for(; set_iter!=eg1.end(); set_iter++)
        cout<<*set_iter<<" ";
    cout<<endl;
//使用size()函数可以获得当前元素个数
    cout<<"Now there are "<<eg1.size()<<" elements in the set eg1"<<endl;
    if(eg1.find(200)==eg1.end())//find()函数可以查找元素是否存在
        cout<<"200 isn't in the set eg1"<<endl;

    set<int>eg2;
    for(int i=6; i<15; i++)
        eg2.insert(i);
    cout<<"Set named eg2:"<<endl;
    for(set_iter=eg2.begin(); set_iter!=eg2.end(); set_iter++)
        cout<<*set_iter<<" ";
    cout<<endl;
//获得两个set的并
    set<int>eg3;
    cout<<"Union:";
    set_union(eg1.begin(),eg1.end(),eg2.begin(),eg2.end(),
              insert_iterator<set<int> >(eg3,eg3.begin()));//注意第五个参数的形式
    copy(eg3.begin(),eg3.end(),ostream_iterator<int>(cout," "));
    cout<<endl;
//获得两个set的交，注意进行集合操作之前接收结果的set要调用clear()函数清空一下
    eg3.clear();
    set_intersection(eg1.begin(),eg1.end(),eg2.begin(),eg2.end(),insert_iterator<set<int> >(eg3,eg3.begin()));
    cout<<"Intersection:";
    copy(eg3.begin(),eg3.end(),ostream_iterator<int>(cout," "));
    cout<<endl;
//获得两个set的差
    eg3.clear();
    set_difference(eg1.begin(),eg1.end(),eg2.begin(),eg2.end(),insert_iterator<set<int> >(eg3,eg3.begin()));
    cout<<"Difference:";
    copy(eg3.begin(),eg3.end(),ostream_iterator<int>(cout," "));
    cout<<endl;
//获得两个set的对称差，也就是假设两个集合分别为A和B那么对称差为AUB-A∩B
    eg3.clear();
    set_symmetric_difference(eg1.begin(),eg1.end(),eg2.begin(),eg2.end(),insert_iterator<set<int> >(eg3,eg3.begin()));
    copy(eg3.begin(),eg3.end(),ostream_iterator<int>(cout," "));
    cout<<endl;
    return 0;
}

(3)multiset

#include <algorithm>
#include<set>
#include<iterator>
#include<iostream>
using namespace std;
int main()
{
    multiset<int>eg1;
//插入
    eg1.insert(1);
    eg1.insert(100);
    eg1.insert(5);
    eg1.insert(1);//是否插入
    eg1.insert(10);
    eg1.insert(9);
//遍历set，可以发现元素是有序的
    multiset<int>::iterator set_iter=eg1.begin();
    cout<<"Set named eg1:"<<endl;
    for(; set_iter!=eg1.end(); set_iter++)
        cout<<*set_iter<<" ";
    cout<<endl;
//使用size()函数可以获得当前元素个数
    cout<<"Now there are "<<eg1.size()<<" elements in the set eg1"<<endl;
    if(eg1.find(200)==eg1.end())//find()函数可以查找元素是否存在
        cout<<"200 isn't in the set eg1"<<endl;
    return 0;
}

(4)理解map

#include <algorithm>
#include<map>
#include<iterator>
#include<iostream>
#include<cstring>
using namespace std;
struct ltstr
{
    bool operator()(const char* s1, const char* s2) const
    {
        return strcmp(s1, s2) < 0;
    }
};

int main()
{
    map<const char*, int, ltstr> months;

    months["january"] = 31;
    months["february"] = 28;
    months["march"] = 31;
    months["april"] = 30;
    months["may"] = 31;
    months["june"] = 30;
    months["july"] = 31;
    months["august"] = 31;
    months["september"] = 30;
    months["october"] = 31;
    months["november"] = 30;
    months["december"] = 31;

    cout << "june -> " << months["june"] << endl;
    map<const char*, int, ltstr>::iterator cur  = months.find("june");
    map<const char*, int, ltstr>::iterator prev = cur;
    map<const char*, int, ltstr>::iterator next = cur;
    ++next;
    --prev;
    cout << "Previous (in alphabetical order) is " << (*prev).first << endl;
    cout << "Next (in alphabetical order) is " << (*next).first << endl;
    return 0;
}

(5)map再例

#include <map>
#include <iostream>

using namespace std;

int main( )
{
    map <int, int> m1, m2, m3;
    map <int, int>::iterator m1_Iter;

    m1.insert ( pair <int, int>  ( 1, 10 ) );
    m1.insert ( pair <int, int>  ( 2, 20 ) );
    m1.insert ( pair <int, int>  ( 3, 30 ) );
    m2.insert ( pair <int, int>  ( 10, 100 ) );
    m2.insert ( pair <int, int>  ( 20, 200 ) );
    m3.insert ( pair <int, int>  ( 30, 300 ) );

    cout << "The original map m1 is:";
    for ( m1_Iter = m1.begin( ); m1_Iter != m1.end( ); m1_Iter++ )
        cout << " " << m1_Iter->second;
    cout   << "." << endl;

    // This is the member function version of swap
    //m2 is said to be the argument map; m1 the target map
    m1.swap( m2 );

    cout << "After swapping with m2, map m1 is:";
    for ( m1_Iter = m1.begin( ); m1_Iter != m1.end( ); m1_Iter++ )
        cout << " " << m1_Iter -> second;
    cout  << "." << endl;
    cout << "After swapping with m2, map m2 is:";
    for ( m1_Iter = m2.begin( ); m1_Iter != m2.end( ); m1_Iter++ )
        cout << " " << m1_Iter -> second;
    cout  << "." << endl;
    // This is the specialized template version of swap
    swap( m1, m3 );

    cout << "After swapping with m3, map m1 is:";
    for ( m1_Iter = m1.begin( ); m1_Iter != m1.end( ); m1_Iter++ )
        cout << " " << m1_Iter -> second;
    cout   << "." << endl;
    return 0;
}

(6)map三例

#include <algorithm>
#include<map>
#include<iterator>
#include<iostream>
#include<cstring>
using namespace std;

int main()
{
    map<char,int> mymap;
    mymap['a']=10;
    mymap['b']=60;
    mymap['c']=30;
    mymap['d']=90;
    mymap['e']=50;

    map<char,int> second(mymap);
    map<char,int> third(mymap.begin(),mymap.end());
    map<char,int>::key_compare key_comp;
    map<char,int>::iterator it;
    it=mymap.begin();
    for (;it!=mymap.end();it++)
    {
        cout<<it->first<<":"<<it->second<<endl;
    }
    cout<<"================================="<<endl;
    second.clear();
    second['a']=1002;
    second['b']=10023;
    while (!second.empty())
    {
        cout << second.begin()->first << " => ";
        cout << second.begin()->second << endl;
        second.erase(second.begin());
    }
    cout<<"================================="<<endl;
    mymap.insert(pair<char,int>('f',100) );
    mymap.insert(pair<char,int>('g',200) );
    cout<<"f => " <<mymap.find('f')->second<<endl;
    cout<<"g => " <<mymap.find('g')->second<<endl;

    cout<<"================================="<<endl;
    key_comp=mymap.key_comp();
    cout << "mymap contains:\n";

    char highest=mymap.rbegin()->first;     // key value of last element

    it=mymap.begin();
    do {
        cout << (*it).first << " => " << (*it).second << endl;
    } while ( key_comp((*it++).first, highest) );

    cout << endl;
    return 0;
}