C++/Map Multimap/map find

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find all elements in a map by value

<source lang="cpp">

  1. include <algorithm>
  2. include <functional>
  3. include <iomanip>
  4. include <iostream>
  5. include <map>
  6. include <string>
  7. include <utility>
  8. 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};
  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;
  const PC::PC_type desired_type = PC::IBM;
  // find all elements by value
  bool found = false;
  for( site = sold.begin(); site != sold_end; ++site )
     if( site->second.appliance() == desired_type ){
        found = true;
        site->second.print();
     }
  if( !found )
     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; } 



 </source>


Find product in a map by its number

<source lang="cpp">

  1. include <algorithm>
  2. include <functional>
  3. include <iomanip>
  4. include <iostream>
  5. include <map>
  6. include <string>
  7. include <utility>
  8. 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};
  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+3, 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();
  const int desired_serial = 33447;
  site = sold.find( desired_serial );
  if( site != sold_end )
     site->second.print();
  else
     cout << "There is no appliance with serial number " << desired_serial << endl;

} inline bool greater_model( const pair<PC::PC_type,PC> p,int min_model ) { return p.second.model() >= min_model; } 



 </source>


Find product in a map by its type

<source lang="cpp">

  1. include <algorithm>
  2. include <functional>
  3. include <iomanip>
  4. include <iostream>
  5. include <map>
  6. include <string>
  7. include <utility>
  8. 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};
  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();
  const PC::PC_type desired_type = PC::IBM;
  
  for( site = sold.begin(); site != sold_end; ++site )
     if( site->second.appliance() == desired_type )
        break;
  if( site != sold_end )
     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; } 



 </source>


Find the value with a given key

<source lang="cpp">

  1. include <iostream>
  2. 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;

} 


 </source>


Map find

<source lang="cpp">

/* 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.
*/
  1. include <iostream>
  2. include <algorithm>
  3. include <map>

using namespace std; /* function object to check the value of a map element 

*/

template <class K, class V> class value_equals { 

 private:
   V value;
 public:
   // constructor (initialize value to compare with)
   value_equals (const V& v)
    : value(v) {
   }
   // comparison
   bool operator() (pair<const K, V> elem) {
       return elem.second == value;
   }

}; int main() { 

   typedef map<float,float> FloatFloatMap;
   FloatFloatMap coll;
   FloatFloatMap::iterator pos;
   // fill container
   coll[1]=7;
   coll[2]=4;
   coll[3]=2;
   coll[4]=3;
   coll[5]=6;
   coll[6]=1;
   coll[7]=3;
   // search an element with key 3.0
   pos = coll.find(3.0);                     // logarithmic complexity
   if (pos != coll.end()) {
       cout << pos->first << ": "
            << pos->second << endl;
   }

} 

/*

3: 2 

*/       
   
   
 </source>


map: find_if

<source lang="cpp">

/* 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.
*/
  1. include <iostream>
  2. include <algorithm>
  3. include <map>

using namespace std; /* function object to check the value of a map element 

*/

template <class K, class V> class value_equals { 

 private:
   V value;
 public:
   // constructor (initialize value to compare with)
   value_equals (const V& v)
    : value(v) {
   }
   // comparison
   bool operator() (pair<const K, V> elem) {
       return elem.second == value;
   }

}; int main() { 

   typedef map<float,float> FloatFloatMap;
   FloatFloatMap coll;
   FloatFloatMap::iterator pos;
   // fill container
   coll[1]=7;
   coll[2]=4;
   coll[3]=2;
   coll[4]=3;
   coll[5]=6;
   coll[6]=1;
   coll[7]=3;
   // search an element with value 3.0
   pos = find_if(coll.begin(),coll.end(),    // linear complexity
                 value_equals<float,float>(3.0));
   if (pos != coll.end()) {
       cout << pos->first << ": "
            << pos->second << endl;
   }

} /* 4: 3 

*/        
   
   
 </source>


map find with custom object

<source lang="cpp">

  1. include <map>
  2. 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);
 map<int, Data>::iterator it = dataMap.find(1);
 if (it != dataMap.end()) {
   it->second.setVal(100);
 }
 return (0);

} 


 </source>


map look up

<source lang="cpp">

  1. include <map>
  2. 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);
 dataMap[1].setVal(100);
 return (0);

} 


 </source>
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