map::erase

Removes an element or a range of elements in a map from specified positions or removes elements that match a specified key.

iterator erase(
   iterator _Where
);
iterator erase(
   iterator _First,
   iterator _Last
);
size_type erase(
   const key_type& _Key
);

Parameters

• _Where
  Position of the element to be removed from the map.

• _First
  Position of the first element removed from the map.

• _Last
  Position just beyond the last element removed from the map.

• _Key
  The key value of the elements to be removed from the map.

Return Value

For the first two member functions, a bidirectional iterator that designates the first element remaining beyond any elements removed, or a pointer to the end of the map if no such element exists.

For the third member function, returns the number of elements that have been removed from the map.

Remarks

In some instances, this method might throw an out_of_range exception. This behavior does not conform to the C++ standard.

Example

When compiling this example with the /Wp64 flag or on a 64-bit platform, compiler warning C4267 will be generated. For more information on this warning, see Compiler Warning (level 3) C4267.

// map_erase.cpp
// compile with: /EHsc
#include <map>
#include <iostream>

int main()
{
    using namespace std;
    map<int, int> m1, m2, m3;
    map<int, int>::iterator pIter, Iter1, Iter2;
    int i;
    map<int, int>::size_type n;
    typedef pair<int, int> Int_Pair;

    for (i = 1; i < 5; i++)
    {
        m1.insert(Int_Pair(i, i));
        m2.insert(Int_Pair(i, i*i));
        m3.insert(Int_Pair(i, i-1));
    }

    // The 1st member function removes an element at a given position
    Iter1 = ++m1.begin();
    m1.erase(Iter1);

    cout << "After the 2nd element is deleted, the map m1 is:";
    for (pIter = m1.begin(); pIter != m1.end(); pIter++)
        cout << " " << pIter->second;
    cout << "." << endl;

    // The 2nd member function removes elements
    // in the range [_First, _Last)
    Iter1 = ++m2.begin();
    Iter2 = --m2.end();
    m2.erase(Iter1, Iter2);

    cout << "After the middle two elements are deleted,"
         << " the map m2 is:";
    for (pIter = m2.begin(); pIter != m2.end(); pIter++)
        cout << " " << pIter->second;
    cout << "." << endl;

    // The 3rd member function removes elements with a given _Key
    n = m3.erase(2);

    cout << "After the element with a key of 2 is deleted,\n"
         << "the map m3 is:";
    for (pIter = m3.begin(); pIter != m3.end(); pIter++)
        cout << " " << pIter->second;
    cout << "." << endl;

    // The 3rd member function returns the number of elements removed
    cout << "The number of elements removed from m3 is: "
         << n << "." << endl;

    // The dereferenced iterator can also be used to specify a key
    Iter1 = ++m3.begin();
    m3.erase(Iter1);

    cout << "After another element with a key equal to that"
         << endl;
    cout  << "of the 2nd element is deleted, "
          << "the map m3 is:";
    for (pIter = m3.begin(); pIter != m3.end(); pIter++)
        cout << " " << pIter->second;
    cout << "." << endl;
}

After the 2nd element is deleted, the map m1 is: 1 3 4.
After the middle two elements are deleted, the map m2 is: 1 16.
After the element with a key of 2 is deleted,
the map m3 is: 0 2 3.
The number of elements removed from m3 is: 1.
After another element with a key equal to that
of the 2nd element is deleted, the map m3 is: 0 3.

Requirements

Header: <map>

Namespace: std

See Also

Concepts

map Class

map Members

map::max_size, map::clear, map::erase, and map::size

Standard Template Library