Просмотр исходного текста страницы C++/Map Multimap/pair

==Computing the Median 1==


   
<source lang="cpp">  
#include <algorithm>
#include <iostream>
#include <map>
#include <vector>
using namespace std;
template <class T>
void print(T& c){
   for( typename T::iterator i = c.begin(); i != c.end(); i++ ){
      std::cout << *i << endl;
   }
}
inline
bool second_less( const pair<int,int> a, const pair<int,int> b )
{  
   return a.second < b.second;   
}
int main( )
{
    const int len = 15;
    const int a[len] = { 9, 2, 3, 3, 7, 5, 7, 7, 4, 10, 5, 6, 7, 4, 7 };
    vector<int> v( a, a + len );
    vector<int>::iterator v_end = v.end();
    print( v );
    
    map<int,int> frequency;
    for( vector<int>::iterator i = v.begin(); i != v_end;++i )
        ++frequency[*i];
    
    pair<int,int> mode_pair = *max_element( frequency.begin(),frequency.end(), second_less );
    
    cout << "Mode by method 1: " << mode_pair.first;
    
}
  
    
  </source>


==for each basic==


   
<source lang="cpp">   
#include <algorithm>
#include <map>
#include <iostream>
using namespace std;
void printPair(const pair<int, int>& elem)
{
  cout << elem.first << "->" << elem.second << endl;
}
int main(int argc, char** argv)
{
  map<int, int> myMap;
  myMap.insert(make_pair(4, 40));
  myMap.insert(make_pair(5, 50));
  myMap.insert(make_pair(6, 60));
  myMap.insert(make_pair(7, 70));
  myMap.insert(make_pair(8, 80));
  for_each(myMap.begin(), myMap.end(), &printPair); 
  return (0);
}
  
    
    
  </source>


==Inserting pairs of object into map==


   
<source lang="cpp">   
#include <map> 
#include <iostream> 
#include <string> 
using namespace std; 
int main() 
{ 
  map<string, double> option; 
  option["r"] = 0.1;       
  option["s"] = 0.2;     
  option["K"] = 1.0;       
  option["T"] = 0.7;       
  option["S"] = 1.3;       
  cout << "Size of map: " << option.size() << endl;; 
  map<string, double>::iterator i = option.begin(); 
  while (i != option.end()) 
  { 
    cout << "Element pair [" << (*i).first << "," << (*i).second << "]"; 
    i++; 
  } 
  return 0; 
}
  
    
    
  </source>


==Iterating over the elements of the map and using the current pair option and second elements.==


   
<source lang="cpp">   
#include <map> 
#include <iostream> 
#include <string> 
using namespace std; 
int main() 
{ 
  map<string, double> option; 
  option["r"] = 0.1;       
  option["s"] = 0.2;     
  option["K"] = 1.0;       
  option["T"] = 0.7;       
  option["S"] = 1.3;       
  cout << "Size of map: " << option.size() << endl;; 
  map<string, double>::iterator i = option.begin(); 
  while (i != option.end()) 
  { 
    cout << "Element pair [" << (*i).first << "," << (*i).second << "]"; 
    i++; 
  } 
  return 0; 
}
  
    
    
  </source>


==Map for string key and integer value==


   
<source lang="cpp">   
#include <iostream>
#include <map>
#include <string>
using namespace std;
int main()
{
   map<string, int, less<string> > name_age;
   name_age["A"] = 7;
   name_age["B"] = 39;
   name_age["C"] = 14;
   cout << "A is  "
        << name_age["A"]
        << " years old." << endl;
}
  
    
    
  </source>


==Pass output message function to for_each function==


   
<source lang="cpp">  
#include <algorithm>
#include <iostream>
#include <list>
#include <string>
#include <utility>
using namespace std;
void print_message( const pair<int,string>& message );
int main( )
{
   list< pair< int, string > > message;
   message.push_back( make_pair( 1, "A" ) );
   message.push_back( make_pair( 2, "B" ) );
   message.push_back( make_pair( 3, "C" ) );
   for_each( message.begin(), message.end(), print_message );
}
void print_message( const pair<int,string>& message ){
   cout << message.first << " - " << message.second << endl;
}
  
    
  </source>


==print the maximum number of <key,data> pairs that DateMap can hold==


   
<source lang="cpp">   
#include <map>
#include <iostream>
#include <string>
using namespace std;
typedef map<string, int> STRING2INT;
int main(void)
{
    STRING2INT DateMap;
    STRING2INT::iterator DateIterator;
    string DateBuffer;
    cout << "DateMap is capable of holding " << DateMap.max_size()
         << " <string,int> pairs" << endl;
 }
  
    
    
  </source>


==Put pairs to map with insert==


   
<source lang="cpp">   
#include <iostream>
#include <map>
using namespace std;
   
int main()
{
  map<char, int> m;
  int i;
   
  for(i=0; i<26; i++) {
    m.insert(pair<char, int>("A"+i, 65+i));
  }
   
  return 0;
}
  
    
    
  </source>


==Sort a list of int and string pairs==


   
<source lang="cpp">  
#include <algorithm>
#include <iostream>
#include <list>
#include <string>
#include <utility>
using namespace std;
void print_message( const pair<int,string>& message );
int main( )
{
   list< pair< int, string > > message;
   message.push_back( make_pair( 1, "A" ) );
   message.push_back( make_pair( 2, "B" ) );
   message.push_back( make_pair( 3, "C" ) );
   for_each( message.begin(), message.end(), print_message );
   message.sort();
   for_each( message.begin(), message.end(), print_message );
}
void print_message( const pair<int,string>& message ){
   cout << message.first << " - " << message.second << endl;
}
  
    
  </source>


==Use map to store the value of the month name and its day number==


   
<source lang="cpp">   
#include <map>
#include <iostream>
#include <string>
using namespace std;
class ltstr{
  public:
    bool operator()(const char* s1, const char* s2) const
     { return (strcmp(s1, s2) < 0);}
};
int main(void)
{
  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;
}
  
    
    
  </source>