C++/Map Multimap/map iterator
Версия от 14:21, 25 мая 2010; (обсуждение)
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;
}
}