[STL基础]multimap多级映射

multimap与map的不同就是：multimap允许关键字key重复，multimap不允许用数组的方式进行赋值

    网上实例

#include <string>#include <map>  #include <conio.h>#include<iostream>using namespace std;   //定义及初始化；没有返回值，或voidvoid test0(){  multimap<int,string> first;first.insert(pair<int,string>(3,"hello"));multimap<int,string> second(first);//拷贝构造函数multimap<int,string> third(first.begin(),first.end());//区间构造函数}//增加删除元素；返回值是void,除erase()的返回值是iterator外void test1(){  //first insert 用insert()函数插入pair数据multimap<char,int> myfirst;myfirst.insert(pair<char,int>('a',100)); //second insert 用insert()函数插入value_type数据myfirst.insert(map<char,int>::value_type('f',50)); //可以用map<char,int>也可以用multimap<char,int>myfirst.insert(map<char,int>::value_type('f',60));  // //third insert 使用数组方式插入数据// myfirst['w']=60; //fourth insert 在iterator位置上插入pair数据multimap<char,int>::iterator ite=myfirst.begin();myfirst.insert(ite,pair<char,int>('b',300));  //比map插入数据方式少了：使用数组方式插入数据cout<<"myfirst\n";for (multimap<char,int>::iterator iter=myfirst.begin();iter!=myfirst.end();iter++){cout<<iter->first<<"=>"<<iter->second<<endl;//a=>100//b=>300//f=>50//f=>60} multimap<int,int> mymap;mymap.insert(multimap<int,int>::value_type(3,30));mymap.insert(multimap<int,int>::value_type(3,100)); mymap.clear();//全部删除mymap.insert(multimap<int,int>::value_type(3,30));mymap.insert(multimap<int,int>::value_type(3,100));while(!mymap.empty()){cout<<mymap.begin()->first<<"=>"<<mymap.begin()->second<<endl;//3=>30//3=>100mymap.erase(mymap.begin());//删除iterator}multimap<char,int> first;multimap<char,int>::iterator it;first.insert(pair<char,int>('a',12));first.insert(pair<char,int>('c',100));first.insert(pair<char,int>('d',12));first.insert(pair<char,int>('a',120));first.insert(pair<char,int>('f',123));first.insert(pair<char,int>('f',18));first.insert(pair<char,int>('a',169)); it=first.find('a');//找到第一个关键字a时就返回 first.erase(it); //用iterator删除，it必须存在， first.erase('f');//用关键字删除，删除其所有的关键字 it=first.find('d'); first.erase(it,first.end());//成片删除cout<<"--------------erase-------------\n";for (it=first.begin();it!=first.end();it++){cout<<it->first<<"=>"<<it->second<<endl;//a=>120//a=>169//c=>100}//与map不同的是：添加方面：multimap少了使用数组添加数据对的方式//                          删除方面：multimap使用关键子删除时，其删除的是其所有的相同的关键字}//访问获取元素；返回值是Type Tvoid test2(){  //map，multimap都是通过iterator的first，second属性来访问其数据multimap<char,int> first; first.insert(multimap<char,int>::value_type('a',30));first.insert(multimap<char,int>::value_type('c',100));  cout<<"a=>"<<first.begin()->second<<endl;//a=>30cout<<"c=>"<<first.find('c')->second<<endl;//c=>100//cout<<"w=>"<<first.find('w')->second<<endl;//当关键字不存在时，运行出现错误multimap<int,int> a;a.insert(pair<int,int>(1,11));a.insert(pair<int,int>(2,12));a.insert(pair<int,int>(3,13));a.insert(pair<int,int>(3,21));a.insert(pair<int,int>(2,22));a.insert(pair<int,int>(1,31));a.insert(pair<int,int>(4,32));cout<<"begin-----按关键字已经排好序了"<<endl;for (multimap<int,int>::iterator it=a.begin();it!=a.end();it++){cout<<it->first<<"=>"<<it->second<<endl;//1=>11//1=>31//2=>12//2=>22//3=>13//3=>21//4=>32}multimap<int,int>::iterator p_map;pair<multimap<int,int>::iterator, multimap<int,int>::iterator> ret;cout<<"输出相同的数据---"<<endl;for(p_map = a.begin() ; p_map != a.end();){cout<<p_map->first<<" =>";ret = a.equal_range(p_map->first);for(p_map = ret.first; p_map != ret.second; ++p_map)cout<<" "<< (*p_map).second;cout<<endl;//1 => 11 31//2 => 12 22//3 => 13 21//4 => 32}//map，multimap都是通过iterator的first，second属性来访问其数据}//返回迭代器；返回值是iterator，或reverse_iteratorvoid test3(){ multimap<char,int> mymap;mymap.insert(pair<char,int>('b',100));mymap.insert(pair<char,int>('a',200));mymap.insert(pair<char,int>('c',500)); mymap.insert(pair<char,int>('b',500)); multimap<char,int>::iterator iter=mymap.begin();for (;iter!=mymap.end();iter++){cout<<iter->first<<"=>"<<iter->second<<endl;//a=>200//b=>100//b=>500//c=>500} cout<<"----reverse_iterator----"<<endl;multimap<char,int>::reverse_iterator riter=mymap.rbegin();for (;riter!=mymap.rend();++riter){ cout<<riter->first<<"=>"<<riter->second<<endl;//c=>500//b=>500//b=>100//a=>200}//与map完全相同} //其他void test4(){  multimap<char,int>mymap,second;mymap.insert(pair<char,int>('a',101));mymap.insert(pair<char,int>('b',202));mymap.insert(pair<char,int>('c',303));mymap.insert(pair<char,int>('d',404));mymap.insert(pair<char,int>('a',123)); for (char c='a';c<'h';c++){cout<<c;if (mymap.count(c)>0){cout<<" is an element of mymap.\n";//a,b,c,d}elsecout<<" is not an element of mymap.\n";//d,e,f,g}cout<<"mymap.size() is "<<mymap.size()<<endl;//5second.insert(pair<char,int>('x',11));second.insert(pair<char,int>('y',22));second.insert(pair<char,int>('z',33)); second.insert(pair<char,int>('y',321)); second.swap(mymap);cout<<"mymap-----\n";for (multimap<char,int>::iterator it=mymap.begin();it!=mymap.end();it++){cout<<it->first<<"=>"<<it->second<<endl;//x=>11//y=>22//y=>321//z=>33}cout<<"second-----\n";for (multimap<char,int>::iterator it=second.begin();it!=second.end();it++){cout<<it->first<<"=>"<<it->second<<endl;//a=>101//a=>123//b=>202//c=>303//d=>404}//equal_range()：返回pair(iterator,iterator),pair中的第一个迭代器是lower_bound()返回的迭代器，pair中的第二个迭代器是upper_bound()返回的迭代器，如果两个迭代器相等，则说明map中不存在这个关键字pair<multimap<char,int>::iterator,multimap<char,int>::iterator> ret=mymap.equal_range('y');cout<<"lower bound points to: "<<ret.first->first<<"=>"<<ret.first->second<<endl;//y=>22，当关键字y不存在时，则输出begin()->first,begin()->second;还有就是ret.second->first不存在！！！cout<<"upper bound points to: "<<ret.second->first<<"=>"<<ret.second->second<<endl;//z=>33,必须确保关键字y后面有别的不同于y的关键字multimap<char,int>::iterator itlow,itup;//lower_bound():返回是iterator，返回要查找关键字的下界(是一个迭代器)//upper_bound():返回是iterator，返回要查找关键字的上界(是一个迭代器)itlow=second.lower_bound('b');//itlow points to bitup=second.upper_bound('c');//itup points to d (not c)second.erase(itlow,itup);//删除[itlow,itup)cout<<"itlow+++++++itup\n";for (multimap<char,int>::iterator it=second.begin();it!=second.end();it++){cout<<it->first<<"=>"<<it->second<<endl; //a=>101//a=>123//d=>404}second.insert(pair<char,int>('p',505));multimap<char,int>::key_compare mycomp=second.key_comp();char highest=second.rbegin()->first;multimap<char,int>::iterator item=second.begin();cout<<"key_compare\n";do {cout<<item->first<<"=>"<<item->second<<endl; //a=>101//a=>123 //d=>404//p=>505}while(mycomp((*item++).first,highest));cout<<"value_compare\n";pair<char,int> high=*second.rbegin();multimap<char,int>::iterator io=second.begin();do {cout<<io->first<<"=>"<<io->second<<endl; //a=>101//a=>123 //d=>404//p=>505} while (second.value_comp()(*io++,high));//其所有函数的功能即用法都有map相同} //遍历map中的数据void test5(){  //1.使用前向迭代器//2.使用相反迭代器//------没有了3.使用数组(不完全正确，当数据插入时键值完全顺序才正确，不然会出现二叉树的输出结果)multimap<int,int> mymap;mymap.insert(multimap<int,int>::value_type(3,30));mymap.insert(multimap<int,int>::value_type(3,100));mymap.insert(multimap<int,int>::value_type(5,50)); mymap.insert(multimap<int,int>::value_type(1,10));  multimap<int,int>::iterator iter=mymap.begin();for (;iter!=mymap.end();iter++){cout<<iter->first<<"=>"<<iter->second<<endl;//1=>10//3=>30//3=>100//5=>50} cout<<"----reverse_iterator----"<<endl;multimap<int,int>::reverse_iterator riter=mymap.rbegin();for (;riter!=mymap.rend();++riter){ cout<<riter->first<<"=>"<<riter->second<<endl;//5=>50//3=>100//3=>30//0=>10}cout<<"mymap size:"<<mymap.size()<<endl;//4    //与map相比：少了数组遍历} void Test(char h){cout<<"press key===="<<h<<endl;switch(h){ case '0':  test0();break;case '1':  test1();break;case '2':  test2();break;case '3':  test3();break;case '4':  test4();break;case '5':  test5();break; case 27:case 'q':exit(0);break; default:cout<<"default "<<h<<endl;break;}}void main(){while(1){Test(getch());} }