std::unordered_map::begin(size_type), std::unordered_map::cbegin(size_type)

From cppreference.com

local_iterator begin( size_type n );
(since C++11)
const_local_iterator begin( size_type n ) const;
(since C++11)
const_local_iterator cbegin( size_type n ) const;
(since C++11)

Returns an iterator to the first element of the bucket with index n.

Parameters

n - the index of the bucket to access

Return value

Iterator to the first element.

Complexity

Constant.

See also

returns an iterator to the end of the specified bucket
(public member function)