C++ Tutorial/map multimap/map insert

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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"] << "\"";
 
}
Источник — «http://cppe.ru/index.php?title=C%2B%2B_Tutorial/map_multimap/map_insert&oldid=2088»