第16周 范型程序补充之map用法



*Copyright(c) 2016.烟台大学计算机与控制工程学院
*ALL rights  reserved.
*文件名称：main.cpp
*作者：孙亚茹
*完成日期：2016年6月17日
*问题描述：阅读程序，体会结果。
*//

（1）

#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;}

（2）

#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;}

（3）

#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;}

总结：

          map和multimap的区别和set和multiset的区别一样，都是带multi的可以有元素的重复。