C++ Tutorial/map multimap/pair — различия между версиями
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Текущая версия на 10:28, 25 мая 2010
Содержание
- 1 Assign value directly to first and second
- 2 Create a pair object that holds the result of insert()
- 3 Create a pair object that will contain the result of a call to insert()
- 4 Default constructor for pair
- 5 Sort a vector of pairs
- 6 Use make_pair() function to create a pair
- 7 Use operator of equal (=)
- 8 Use operator of less than (
- 9 Using a Pair to store int and string
- 10 Using copy constructor to create another pair
- 11 Vector of pair
Assign value directly to first and second
#include <utility>
#include <string>
#include <iostream>
using namespace std;
int main(int argc, char** argv)
{
pair<string, int> myPair("hello", 5), myOtherPair;
myOtherPair.first = "hello";
myOtherPair.second = 6;
return (0);
}Create a pair object that holds the result of insert()
#include <iostream>
#include <string>
#include <map>
#include <utility>
using namespace std;
void show(const char *msg, map<string, string> mp);
int main() {
map<string, string> phonemap;
phonemap["A"] = "444-555-1234";
phonemap["B"] = "555-555-6576";
phonemap["C"] = "555-555-9843";
show("Here is the original map: ", phonemap);
cout << endl;
// Create a pair object that will contain the result of a call to insert().
pair<map<string, string>::iterator, bool> result;
// Use insert() to add an entry.
result = phonemap.insert(pair<string, string>("Jay", "555-9999"));
if(result.second) cout << "Jay added.\n";
show("phonemap after adding Jay: ", phonemap);
return 0;
}
// Display the contents of a map<string, string> by using an iterator.
void show(const char *msg, map<string, string> mp) {
map<string, string>::iterator itr;
cout << msg << endl;
for(itr=mp.begin(); itr != mp.end(); ++itr)
cout << " " << itr->first << ": " << itr->second << endl;
cout << endl;
}Create a pair object that will contain the result of a call to insert()
#include <iostream>
#include <string>
#include <map>
#include <utility>
using namespace std;
void show(const char *msg, map<string, string> mp);
int main() {
map<string, string> phonemap;
phonemap["A"] = "444-555-1234";
phonemap["B"] = "555-555-6576";
phonemap["C"] = "555-555-9843";
show("Here is the original map: ", phonemap);
phonemap["B"] = "555 555-5555";
cout << "New number: " << phonemap["B"] << endl;
// Create a pair object that will contain the result of a call to insert().
pair<map<string, string>::iterator, bool> result;
// Use insert() to add an entry.
result = phonemap.insert(pair<string, string>("J", "555-9999"));
if(result.second) cout << "J added.";
show("phonemap after adding J: ", phonemap);
return 0;
}
// Display the contents of a map<string, string> by using an iterator.
void show(const char *msg, map<string, string> mp) {
map<string, string>::iterator itr;
cout << msg << endl;
for(itr=mp.begin(); itr != mp.end(); ++itr)
cout << " " << itr->first << ": " << itr->second << endl;
cout << endl;
}Default constructor for pair
#include <utility>
#include <string>
#include <iostream>
using namespace std;
int main(int argc, char** argv)
{
pair<string, int> myPair("hello", 5), myOtherPair;
return (0);
}Sort a vector of pairs
#include <algorithm>
#include <iostream>
#include <iterator>
#include <string>
#include <vector>
#include <utility>
using namespace std;
typedef pair<int,string> Pair;
inline bool less_than_second( const Pair& b1, const Pair& b2 ){
return b1.second < b2.second;
}
int main(){
const char* names[] = { "A","B", "C", "D","E" };
const int values[] = { 18, 20, 26, 30, 41 };
const int num_pairs = sizeof( names ) / sizeof( names[0] );
vector<Pair> pair( num_pairs );
transform( values, values+num_pairs, names,pair.begin(), make_pair<int,string> );
sort( pair.begin(), pair.end() );
sort( pair.begin(), pair.end(), less_than_second );
vector<Pair>::const_iterator pair_end = pair.end();
for( vector<Pair>::const_iterator i = pair.begin();
i != pair_end; ++i )
cout << i->second << " - $" << i->first << " values\n";
}Use make_pair() function to create a pair
#include <utility>
#include <string>
#include <iostream>
using namespace std;
int main(int argc, char** argv){
pair<string, int> myPair("hello", 5), myOtherPair;
myOtherPair.first = "hello";
myOtherPair.second = 6;
pair<string, int> myThirdPair(myOtherPair);
pair<int, int> aPair = make_pair(5, 10);
return (0);
}Use operator of equal (=)
#include <utility>
#include <string>
#include <iostream>
using namespace std;
int main(int argc, char** argv)
{
pair<string, int> myPair("hello", 5), myOtherPair;
myOtherPair.first = "hello";
myOtherPair.second = 6;
pair<string, int> myThirdPair(myOtherPair);
if (myOtherPair == myThirdPair) {
cout << "myOtherPair is equal to myThirdPair\n";
} else {
cout << "myOtherPair is not equal to myThirdPair\n";
}
pair<int, int> aPair = make_pair(5, 10);
return (0);
}Use operator of less than (
#include <utility>
#include <string>
#include <iostream>
using namespace std;
int main(int argc, char** argv){
pair<string, int> myPair("hello", 5), myOtherPair;
myOtherPair.first = "hello";
myOtherPair.second = 6;
pair<string, int> myThirdPair(myOtherPair);
if (myPair < myOtherPair) {
cout << "myPair is less than myOtherPair\n";
} else {
cout << "myPair is greater than or equal to myOtherPair\n";
}
return (0);
}Using a Pair to store int and string
#include <algorithm>
#include <iostream>
#include <iterator>
#include <string>
#include <vector>
#include <utility>
using namespace std;
typedef pair<int,string> Pair;
inline bool less_than_second( const Pair& b1, const Pair& b2 ){
return b1.second < b2.second;
}
int main( )
{
const char* names[] = { "A","B", "C", "D","E" };
const int values[] = { 18, 20, 26, 30, 41 };
const int num_pairs = sizeof( names ) / sizeof( names[0] );
vector<Pair> pair( num_pairs );
transform( values, values+num_pairs, names,pair.begin(), make_pair<int,string> );
if( pair[1].first > pair[3].first )
cout << pair[1].second << " > " << pair[3].second << endl;
else if( pair[1].first == pair[3].first )
cout << pair[1].second << " == " << pair[3].second << endl;
else
cout << pair[1].second << " < " << pair[3].second << endl;
sort( pair.begin(), pair.end() );
vector<Pair>::const_reverse_iterator pair_rend = pair.rend();
for( vector<Pair>::const_reverse_iterator i= pair.rbegin(); i != pair_rend; ++i )
cout << i->first << " - " << i->second;
sort( pair.begin(), pair.end(), less_than_second );
vector<Pair>::const_iterator pair_end = pair.end();
for( vector<Pair>::const_iterator i = pair.begin();
i != pair_end; ++i )
cout << i->second << " - $" << i->first << " values\n";
}Using copy constructor to create another pair
#include <utility>
#include <string>
#include <iostream>
using namespace std;
int main(int argc, char** argv)
{
pair<string, int> myPair("hello", 5), myOtherPair;
// assign directly to first and second
myOtherPair.first = "hello";
myOtherPair.second = 6;
// copy construcor
pair<string, int> myThirdPair(myOtherPair);
return (0);
}Vector of pair
#include <algorithm>
#include <iostream>
#include <iterator>
#include <string>
#include <vector>
#include <utility>
using namespace std;
typedef pair<int,string> Pair;
inline bool less_than_second( const Pair& b1, const Pair& b2 ){
return b1.second < b2.second;
}
int main( )
{
const char* names[] = { "A","B", "C", "D","E" };
const int values[] = { 18, 20, 26, 30, 41 };
const int num_pairs = sizeof( names ) / sizeof( names[0] );
vector<Pair> pair( num_pairs );
transform( values, values+num_pairs, names,pair.begin(), make_pair<int,string> );
sort( pair.begin(), pair.end() );
vector<Pair>::const_reverse_iterator pair_rend = pair.rend();
for( vector<Pair>::const_reverse_iterator i= pair.rbegin(); i != pair_rend; ++i )
cout << i->first << " - " << i->second;
sort( pair.begin(), pair.end(), less_than_second );
vector<Pair>::const_iterator pair_end = pair.end();
for( vector<Pair>::const_iterator i = pair.begin();
i != pair_end; ++i )
cout << i->second << " - $" << i->first << " values\n";
}