unordered_multiset reserve() in C++ STL (original) (raw)

Last Updated : 23 Jul, 2019

The reserve() function of unordered_multiset sets the number of buckets in the container (bucket_count) to the most appropriate to contain at least n elements. If n is greater than the current bucket_count multiplied by the max_load_factor, the container's bucket_count is increased and a rehash is forced. If n is lower than that, the function may have no effect.Syntax:

void reserve( size_type n );

where size_type is an unsigned integral type.Parameters: This method accepts a mandatory parameter n which is the number of elements requested as minimum capacity.Returns: It does not returns any value. Below are the programs to illustrate reserve() method:Example 1:

CPP `

#include #include

using namespace std;

int main() { unordered_multiset j;

// container invoked
// it reverse the values
j.reserve(5);

// set the values of the container
j.insert(5);
j.insert(6);
j.insert(7);

cout << "The values in unordered_multiset :";
for (const int& x : j)
    cout << " " << x;

return 0;

}

`

Output:

The values in unordered_multiset : 7 6 5

Example 2:

CPP `

#include #include

using namespace std;

int main() { unordered_multiset j;

// container invoked
// it reverse the values
j.reserve(5);

// set the values of the container
j.insert("Geeks");
j.insert("forGeeks");
j.insert("GeeksforGeeks");

cout << "The values in unordered_multiset :";
for (const string& x : j)
    cout << " " << x;

return 0;

}

`

Output:

The values in unordered_multiset : GeeksforGeeks forGeeks Geeks