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Returns the number of elements in the map.

size_type size( ) const;

The current length of the map.

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

int main()
    using namespace std;
    map<int, int> m1, m2;
    map<int, int>::size_type i;
    typedef pair<int, int> Int_Pair;

    m1.insert(Int_Pair(1, 1));
    i = m1.size();
    cout << "The map length is " << i << "." << endl;

    m1.insert(Int_Pair(2, 4));
    i = m1.size();
    cout << "The map length is now " << i << "." << endl;
The map length is 1.
The map length is now 2.

Header: <map>

Namespace: std

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