C++ Tutorial/map multimap/map insert
Версия от 14:21, 25 мая 2010; (обсуждение)
Содержание
- 1 Duplicate keys are not allowed in a map
- 2 Insert a pair object directly
- 3 Insert a pair using function make_pair
- 4 Insert characters into map.
- 5 Insert key-value pairs into the map using value_type
- 6 Insert using an array-like syntax for inserting key-value pairs
- 7 Insert value pair to map
- 8 Use insert() to add an entry
- 9 use subscript operator to write value to a map
Duplicate keys are not allowed in a map
#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;
// Now, change the phone number for Ken.
phonemap["B"] = "555 555-5555";
cout << "New number for Ken: " << phonemap["Ken"] << "\n\n";
// Create a pair object that will contain the result of a call to insert().
pair<map<string, string>::iterator, bool> result;
// Duplicate keys are not allowed, as the following proves.
result = phonemap.insert(pair<string, string>("B", "555-1010"));
if(result.second)
cout << "Duplicate added! Error!";
else
cout << "Duplicate not allowed.\n";
show("phonemap after attempt to add duplicate key: ", 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;
}Insert a pair object directly
#include <map>
#include <iostream>
using namespace std;
typedef map <int, string> MAP_INT_STRING;
typedef multimap <int, string> MMAP_INT_STRING;
int main ()
{
MAP_INT_STRING mapIntToString;
mapIntToString.insert (pair <int, string> (1000, "One Thousand"));
cout << "The map contains " << mapIntToString.size ();
cout << " key-value pairs. " << endl;
cout << "The elements in the map are: " << endl;
return 0;
}Insert a pair using function make_pair
#include <map>
#include <iostream>
using namespace std;
typedef map <int, string> MAP_INT_STRING;
typedef multimap <int, string> MMAP_INT_STRING;
int main ()
{
MAP_INT_STRING mapIntToString;
mapIntToString.insert (make_pair (-1, "Minus One"));
cout << "The map contains " << mapIntToString.size ();
cout << " key-value pairs. " << endl;
cout << "The elements in the map are: " << endl;
return 0;
}Insert characters into map.
#include <iostream>
#include <string>
#include <map>
using namespace std;
int main() {
map<string, int> m;
m.insert(pair<string, int>("A", 100));
m.insert(pair<string, int>("G", 300));
m.insert(pair<string, int>("B", 200));
return 0;
}Insert key-value pairs into the map using value_type
#include <map>
#include <iostream>
using namespace std;
typedef map <int, string> MAP_INT_STRING;
typedef multimap <int, string> MMAP_INT_STRING;
int main ()
{
MAP_INT_STRING mapIntToString;
// Insert key-value pairs into the map using value_type
mapIntToString.insert (MAP_INT_STRING::value_type (3, "Three"));
cout << "The map contains " << mapIntToString.size ();
cout << " key-value pairs. " << endl;
cout << "The elements in the map are: " << endl;
return 0;
}Insert using an array-like syntax for inserting key-value pairs
#include <map>
#include <iostream>
using namespace std;
typedef map <int, string> MAP_INT_STRING;
typedef multimap <int, string> MMAP_INT_STRING;
int main ()
{
MAP_INT_STRING mapIntToString;
// Insert using an array-like syntax for inserting key-value pairs
mapIntToString [1000000] = "One Million";
cout << "The map contains " << mapIntToString.size ();
cout << " key-value pairs. " << endl;
cout << "The elements in the map are: " << endl;
return 0;
}Insert value pair to map
#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
Use insert() to add an entry
#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;
}use subscript operator to write value to a map
#include <algorithm>
#include <iostream>
#include <map>
#include <utility>
using namespace std;
int main( )
{
const char* word[] = { "A", "B", "C", "D","E" };
const char* clue[] = { "a", "b","c", "d","e" };
map<string,string> dictionary1;
transform( word, word+sizeof(word)/sizeof(word[0]), clue,inserter( dictionary1, dictionary1.end() ),make_pair<string,string> );
cout << "There are " << dictionary1.size() << " words in the dictionary\n\n";
cout << "The clue for POPS is \"" << dictionary1["POPS"] << "\"\n"
<< "The clue for TAT is \"" << dictionary1["TAT"] << "\"\n"
<< "The clue for ESPO0 is \"" << dictionary1["ESPO0"] << "\"\n";
cout << "\nThere are " << dictionary1.size() << " words in the dictionary\n\n";
// use subscript operator to write value
dictionary1["ESPO0"] = "Typo in name";
cout << "The clue for ESPO0 is \"" << dictionary1["ESPO0"] << "\"";
}