hash_map::insert
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hash_map::insert

Inserts an element or a range of elements into a hash_map.

pair <iterator, bool> insert(
   const value_type& _Val
);
iterator insert(
   iterator _Where,
   const value_type& _Val
);
template<class InputIterator>
   void insert(
      InputIterator _First,
      InputIterator _Last
   );

Parameters

_Val
The value of an element to be inserted into the hash_map unless the hash_map already contains that element (or, more generally, an element whose key is equivalently ordered).
_Where
A hint regarding the place to start searching for the correct point of insertion.
_First
The position of the first element to be copied from a hash_map.
_Last
The position just beyond the last element to be copied from a hash_map.

Return Value

The first insert member function returns a pair whose bool component returns true if an insertion was make and false if the hash_map already contained an element whose key had an equivalent value in the ordering, and whose iterator component returns the address where a new element was inserted or where the element was already located.

To access the iterator component of a pair pr returned by this member function, use pr.first, and to dereference it, use *(pr.first). To access the bool component of a pair pr returned by this member function, use pr.second, and to dereference it, use *(pr.second).

The second insert member function, the hint version, returns an iterator that points to the position where the new element was inserted into the hash_map.

Remarks

The value_type of an element is a pair, so that the value of an element will be an ordered pair with the first component equal to the key value and the second component equal to the data value of the element.

Insertion can occur in amortized constant time for the hint version of insert, instead of logarithmic time, if the insertion point immediately follows _Where.

The third member function inserts the sequence of element values into a hash_map corresponding to each element addressed by an iterator of in the range [First, Last) of a specified set.

In Visual C++ .NET 2003, members of the <hash_map> and <hash_set> header files are no longer in the std namespace, but rather have been moved into the stdext namespace. See The stdext Namespace for more information.

Example

// hash_map_insert.cpp
// compile with: /EHsc
#include <hash_map>
#include <iostream>

int main( )
{
   using namespace std;
   using namespace stdext;
   hash_map <int, int>::iterator hm1_pIter, hm2_pIter;

   hash_map <int, int> hm1, hm2;
   typedef pair <int, int> Int_Pair;

   hm1.insert ( Int_Pair ( 1, 10 ) );
   hm1.insert ( Int_Pair ( 2, 20 ) );
   hm1.insert ( Int_Pair ( 3, 30 ) );
   hm1.insert ( Int_Pair ( 4, 40 ) );

   cout << "The original key values of hm1 =";
   for ( hm1_pIter = hm1.begin( ); hm1_pIter != hm1.end( ); hm1_pIter++ )
      cout << " " << hm1_pIter -> first;
   cout << "." << endl;

   cout << "The original hash_mapped values of hm1 =";
   for ( hm1_pIter = hm1.begin( ); hm1_pIter != hm1.end( ); hm1_pIter++ )
      cout << " " << hm1_pIter -> second;
   cout << "." << endl;

   pair< hash_map<int,int>::iterator, bool > pr;
   pr = hm1.insert ( Int_Pair ( 1, 10 ) );

   if( pr.second == true )   
   {
      cout << "The element 10 was inserted in hm1 successfully."
           << endl;
   }
   else   
   {
      cout << "The element 10 already exists in hm1\n with a key value of"
           << " ( (pr.first) -> first ) = " << ( pr.first ) -> first 
           << "." << endl;
   }

   // The hint version of insert
   hm1.insert( --hm1.end( ), Int_Pair ( 5, 50 ) );

   cout << "After the insertions, the key values of hm1 =";
   for ( hm1_pIter = hm1.begin( ); hm1_pIter != hm1.end( ); hm1_pIter++ )
      cout << " " << hm1_pIter -> first;
   cout << "," << endl;

   cout << " and the mapped values of hm1 =";
   for ( hm1_pIter = hm1.begin( ); hm1_pIter != hm1.end( ); hm1_pIter++ )
      cout << " " << hm1_pIter -> second;
   cout << "." << endl;

   hm2.insert ( Int_Pair ( 10, 100 ) );

   // The templatized version inserting a range
   hm2.insert( ++hm1.begin( ), --hm1.end( ) );

   cout << "After the insertions, the key values of hm2 =";
   for ( hm2_pIter = hm2.begin( ); hm2_pIter != hm2.end( ); hm2_pIter++ )
      cout << " " << hm2_pIter -> first;
   cout << "," << endl;

   cout << " and the mapped values of hm2 =";
   for ( hm2_pIter = hm2.begin( ); hm2_pIter != hm2.end( ); hm2_pIter++ )
      cout << " " << hm2_pIter -> second;
   cout << "." << endl;
}

Output

The original key values of hm1 = 1 2 3 4.
The original hash_mapped values of hm1 = 10 20 30 40.
The element 10 already exists in hm1
 with a key value of ( (pr.first) -> first ) = 1.
After the insertions, the key values of hm1 = 1 3 5 2 4,
 and the mapped values of hm1 = 10 30 50 20 40.
After the insertions, the key values of hm2 = 2 3 5 10,
 and the mapped values of hm2 = 20 30 50 100.

See Also

hash_map Class | hash_map Members

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