C++ unordered_multiset - bucket() Function

The C++ unordered_multiset::bucket function returns the bucket number of the specified element of the unordered_multiset.

As an unordered_multiset is implemented using hash table where a bucket is a slot in the container's internal hash table to which elements are assigned based on the hash value. Buckets are numbered from 0 to (bucket_count-1). The number of buckets directly influences the load_factor of the container's hash table. The container automatically increases the number of buckets to keep the load_factor below its max_load_factor which causes rehash whenever the number of buckets is increased.

Syntax

C++11

size_type bucket ( const key_type& k ) const;

Parameters

`k`	Specify element whose bucket number is to be looked for.

Return Value

The bucket number of the specified element of the unordered_multiset.

Time Complexity

Constant i.e, Θ(1).

Example:

In the example below, the unordered_multiset::bucket function returns the bucket number of the specified element of uMSet.

#include <iostream>
#include <unordered_set>
using namespace std;
 
int main (){
  unordered_multiset<int> uMSet{10, 20, 30, 10, 20, 40};

  for(const int& x: uMSet)
    cout<<x<<" is in bucket #"<<uMSet.bucket(x)<<".\n";   

  return 0;
}

The output of the above code will be:

40 is in bucket #5.
30 is in bucket #2.
20 is in bucket #6.
20 is in bucket #6.
10 is in bucket #3.
10 is in bucket #3.

❮ C++ <unordered_set> Library