C++/Map Multimap/map iterator — различия между версиями

Текущая версия на 10:25, 25 мая 2010

Содержание

1 const_iterator for map if integer and user-define object
2 const_reverse_iterator from a map
3 Create int string map and print all element pair
4 Get iterator from a map
5 Loop through map and print all the key/value pair
6 Map Iterators
7 Use iterator to loop through map and print all elements
8 Use while to loop through a map

const_iterator for map if integer and user-define object

    
#include <algorithm>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <string>
#include <utility>
#include <vector>
using namespace std;
class PC
{
   public:
   enum PC_type { Dell, HP, IBM, Compaq };
   PC( PC_type appliance = Dell, int model = 220,
      int serial = 0 );
   bool operator<( const PC& rhs ) const;
   PC_type appliance() const;
   int model() const;
   string name() const;
   void print() const;
   int serial() const;
   private:
   PC_type appliance_;
   int model_;
   int serial_;
};
inline
PC::PC( PC::PC_type appliance, int model,
   int serial )
   : appliance_( appliance ), model_( model ), serial_( serial )
{} // empty
inline
bool PC::operator<( const PC& rhs ) const
{ return appliance() < rhs.appliance() ||
   ( appliance() == rhs.appliance() && model() < rhs.model() );
}
inline
PC::PC_type PC::appliance() const
{ return appliance_; }
inline
int PC::model() const
{ return model_; }
string PC::name() const
{
   string what;
   switch( appliance() )
   {
      case Dell:   what = "Dell";               break;
      case HP:     what = "HP";                 break;
      case IBM:    what = "IBM";                break;
      case Compaq: what = "Compaq";             break;
      default:     what = "Unknown appliance";  break;
   }
   return what;
}
inline
void PC::print() const
{
   char oldfill = cout.fill();
   cout << name() << " - Model "
        << model() << ", Serial number " 
        << serial() << endl;
}
inline
int PC::serial() const
{ return serial_; }
bool greater_model( const pair<PC::PC_type,PC> p,int min_model );
int main( )
{
   const PC::PC_type kind[] = { PC::IBM,PC::Dell,PC::HP};
   int num_appliances = 3;
   vector<PC> v;
   for( int i = 0; i < 3; ++i )
      v.push_back( PC( kind[i], i, i ) );
   map<int,PC> sold;
   transform( kind, kind+num_appliances, v.begin(),inserter( sold, sold.end() ),make_pair<int,PC> );
   map<int,PC>::const_iterator sold_end = sold.end();
   map<int,PC>::const_iterator site;
   for( site = sold.begin(); site != sold_end; ++site )
      site->second.print();
}
inline
bool greater_model( const pair<PC::PC_type,PC> p,int min_model )
{ return p.second.model() >= min_model; }

const_reverse_iterator from a map

    
#include <algorithm>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <string>
#include <utility>
#include <vector>
using namespace std;
class PC
{
   public:
   enum PC_type { Dell, HP, IBM, Compaq };
   PC( PC_type appliance = Dell, int model = 220,
      int serial = 0 );
   bool operator<( const PC& rhs ) const;
   PC_type appliance() const;
   int model() const;
   string name() const;
   void print() const;
   int serial() const;
   private:
   PC_type appliance_;
   int model_;
   int serial_;
};
inline
PC::PC( PC::PC_type appliance, int model,
   int serial )
   : appliance_( appliance ), model_( model ), serial_( serial )
{} // empty
inline
bool PC::operator<( const PC& rhs ) const
{ return appliance() < rhs.appliance() ||
   ( appliance() == rhs.appliance() && model() < rhs.model() );
}
inline
PC::PC_type PC::appliance() const
{ return appliance_; }
inline
int PC::model() const
{ return model_; }
string PC::name() const
{
   string what;
   switch( appliance() )
   {
      case Dell:    what = "Dell";               break;
      case HP:      what = "HP";                 break;
      case IBM:     what = "IBM";                break;
      case Compaq:  what = "Compaq";             break;
      default:      what = "Unknown appliance";  break;
   }
   return what;
}
inline
void PC::print() const
{
   char oldfill = cout.fill();
   cout << name() << " - Model "
        << model() << ", Serial number "
        << serial() << endl;
}
inline
int PC::serial() const
{ return serial_; }
bool greater_model( const pair<PC::PC_type,PC> p,int min_model );
int main( )
{
   const PC::PC_type kind[] = { PC::IBM,
      PC::IBM, PC::Dell, PC::HP,
      PC::HP, PC::HP };
   const int num_appliances = 3;
   vector<PC> v;
   for( int i = 0; i < num_appliances; ++i )
      v.push_back( PC( kind[i], i, i ) );
   map<int,PC> sold;
   transform( kind, kind+num_appliances, v.begin(),inserter( sold, sold.end() ),make_pair<int,PC> );
   map<int,PC>::const_iterator sold_end = sold.end();
   map<int,PC>::const_iterator site;
   for( site = sold.begin(); site != sold_end; ++site )
      site->second.print();
   map<int,PC>::const_reverse_iterator reverse_site;
   map<int,PC>::const_reverse_iterator sold_rend = sold.rend();
   const PC::PC_type desired_type = PC::IBM;
   for( reverse_site = sold.rbegin(); reverse_site != sold_rend;++reverse_site )
      if( reverse_site->second.appliance() == desired_type )
         break;
   if( reverse_site != sold_rend )
      reverse_site->second.print();
   else
      cout << "No IBMs sold\n";
}
inline
bool greater_model( const pair<PC::PC_type,PC> p,int min_model )
{ return p.second.model() >= min_model; }

Create int string map and print all element pair

   
 

/* The following code example is taken from the book
 * "The C++ Standard Library - A Tutorial and Reference"
 * by Nicolai M. Josuttis, Addison-Wesley, 1999
 *
 * (C) Copyright Nicolai M. Josuttis 1999.
 * Permission to copy, use, modify, sell and distribute this software
 * is granted provided this copyright notice appears in all copies.
 * This software is provided "as is" without express or implied
 * warranty, and with no claim as to its suitability for any purpose.
 */
#include <iostream>
#include <map>
#include <string>
using namespace std;
int main()
{
    // type of the collection
    typedef multimap<int,string> IntStringMMap;
    IntStringMMap coll;        // container for int/string values
    // insert some elements in arbitrary order
    // - a value with key 1 gets inserted twice
    coll.insert(make_pair(5,"tagged"));
    coll.insert(make_pair(2,"a"));
    coll.insert(make_pair(1,"this"));
    coll.insert(make_pair(4,"of"));
    coll.insert(make_pair(6,"strings"));
    coll.insert(make_pair(1,"is"));
    coll.insert(make_pair(3,"multimap"));
    /* print all element values
     * - iterate over all elements
     * - element member second is the value
     */
    IntStringMMap::iterator pos;
    for (pos = coll.begin(); pos != coll.end(); ++pos) {
        cout << pos->second << " ";
    }
    cout << endl;
}
 /* 
this is a multimap of tagged strings
 */

Get iterator from a map

  
#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));
  }
   
  char ch;
  cout << "Enter key: ";
  cin >> ch;
   
  map<char, int>::iterator p;
 
  p = m.find(ch);
  if(p != m.end())
    cout << "Its ASCII value is  " << p->second;
  else
    cout << "Key not in map.\n";
   
  return 0;
}

Loop through map and print all the key/value pair

   
 
#include <iostream>
using std::cout;
using std::endl;
#include <map> // map class-template definition
int main()
{
   std::map< int, double, std::less< int > > pairs;
   pairs.insert( std::map< int, double, std::less< int > >::value_type( 15, 2.7 ) );
   pairs.insert( std::map< int, double, std::less< int > >::value_type( 30, 111.11 ) );
   pairs.insert( std::map< int, double, std::less< int > >::value_type( 0, 1010.1 ) );
   pairs.insert( std::map< int, double, std::less< int > >::value_type( 10, 22.22 ) );
   pairs.insert( std::map< int, double, std::less< int > >::value_type( 25, 33.333 ) );
   pairs.insert( std::map< int, double, std::less< int > >::value_type( 0, 77.54 ) ); // dup ignored
   pairs.insert( std::map< int, double, std::less< int > >::value_type( 20, 9.345 ) );
   pairs.insert( std::map< int, double, std::less< int > >::value_type( 15, 99.3 ) ); // dup ignored
   cout << "pairs contains:\nKey\tValue\n";
   // use const_iterator to walk through elements of pairs
   for ( std::map< int, double, std::less< int > >::const_iterator iter = pairs.begin();
      iter != pairs.end(); ++iter )
      cout << iter->first << "\t" << iter->second << "\n";
   cout << endl;
   return 0;
}
/* 
pairs contains:
Key     Value
0       1010.1
10      22.22
15      2.7
20      9.345
25      33.333
30      111.11

 */

Map Iterators

  
#include <map>
#include <iostream>
using namespace std;
class Data
{
public:
  Data(int val = 0) { mVal = val; }
  int getVal() const { return mVal; }
  void setVal(int val) {mVal = val; }
protected:
  int mVal;
};
int main(int argc, char** argv)
{
  map<int, Data> dataMap;
  dataMap[1] = Data(4);
  dataMap[1] = Data(6);
  for (map<int, Data>::iterator it = dataMap.begin();
       it != dataMap.end(); ++it) {
    cout << it->second.getVal() << endl;
  }
  return (0);
}

Use iterator to loop through map and print all elements

   
 
/* The following code example is taken from the book
 * "The C++ Standard Library - A Tutorial and Reference"
 * by Nicolai M. Josuttis, Addison-Wesley, 1999
 *
 * (C) Copyright Nicolai M. Josuttis 1999.
 * Permission to copy, use, modify, sell and distribute this software
 * is granted provided this copyright notice appears in all copies.
 * This software is provided "as is" without express or implied
 * warranty, and with no claim as to its suitability for any purpose.
 */
#include <iostream>
#include <map>
#include <string>
using namespace std;
int main()
{
    /* type of the container:
     * - map: elements key/value pairs
     * - string: keys have type string
     * - float: values have type float
     */
    typedef map<string,float> StringFloatMap;
    StringFloatMap coll;
    // insert some elements into the collection
    coll["VAT"] = 0.15;
    coll["Pi"] = 3.1415;
    coll["an arbitrary number"] = 4983.223;
    coll["Null"] = 0;
    /* print all elements
     * - iterate over all elements
     * - element member first is the key
     * - element member second is the value
     */
    StringFloatMap::iterator pos;
    for (pos = coll.begin(); pos != coll.end(); ++pos) {
        cout << "key: \"" << pos->first << "\" "
             << "value: " << pos->second << endl;
    }
}
 /* 
key: "Null" value: 0
key: "Pi" value: 3.1415
key: "VAT" value: 0.15
key: "an arbitrary number" value: 4983.22
 */

Use while to loop through a map

  
#include <map>
#include <iostream>
#include <string>
using namespace std;
typedef map<string, int> STRING2INT;
int main(void)
{
    STRING2INT DateMap;
    STRING2INT::iterator DateIterator;
    string DateBuffer;
    DateMap["January"] = 1;
    DateMap["February"] = 2;
    DateMap["March"] = 3;
    DateMap["April"] = 4;
    DateMap["May"] = 5;
    DateMap["June"] = 6;
    DateMap["July"] = 7;
    DateMap["August"] = 8;
    DateMap["September"] = 9;
    DateMap["October"] = 10;
    DateMap["November"] = 11;
    DateMap["December"] = 12;
    DateIterator = DateMap.end();
    while(DateIterator == DateMap.end())
     {
        cout << "Enter a Month :";
        cin >> DateBuffer;
        if((DateIterator = DateMap.find(DateBuffer)) != DateMap.end())
            cout << (*DateIterator).first << " is Month Number "
                 << (*DateIterator).second << endl;
        else
            cout << "Enter a Valid Month (example: March)" << endl;
     }
}

C++/Map Multimap/map iterator — различия между версиями

Текущая версия на 10:25, 25 мая 2010

Содержание

const_iterator for map if integer and user-define object

const_reverse_iterator from a map

Create int string map and print all element pair

Get iterator from a map

Loop through map and print all the key/value pair

Map Iterators

Use iterator to loop through map and print all elements

Use while to loop through a map

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Версия 14:21, 25 мая 2010 (просмотреть исходный код) (обсуждение) ← Предыдущая правка	Текущая версия на 10:25, 25 мая 2010 (просмотреть исходный код) Admin (обсуждение \| вклад) м (1 версия: Импорт контента...)
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