C++ Unordered_map Library - bucket_size() Function

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Description

The C++ function std::unordered_map::bucket_size() returns the number of elements presents in the n^th bucket.

Declaration

Following is the declaration for std::unordered_map::bucket_size() function form std::unordered_map header.

C++11

size_type bucket_size(size_type n) const;

Parameters

n − Bucket number.

Return value

Returns the total number of elements from current bucket.

Time complexity

Linear i.e. O(n)

Example

The following example shows the usage of std::unordered_map::bucket_size() function.

#include <iostream>
#include <unordered_map>

using namespace std;

int main(void) {
   unordered_map<char, int> um = {
            {'a', 1},
            {'b', 2},
            {'c', 3},
            {'d', 4},
            {'e', 5}
            };

   for (int i = 0; i < um.bucket_count(); ++i)
      cout << "Bucket " << i << " contains "
          << um.bucket_size(i) << " elements." << endl;

   return 0;
}

Let us compile and run the above program, this will produce the following result −

Bucket 0 contains 1 elements.
Bucket 1 contains 1 elements.
Bucket 2 contains 1 elements.
Bucket 3 contains 0 elements.
Bucket 4 contains 0 elements.
Bucket 5 contains 0 elements.
Bucket 6 contains 0 elements.
Bucket 7 contains 0 elements.
Bucket 8 contains 0 elements.
Bucket 9 contains 1 elements.
Bucket 10 contains 1 elements.