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C++ Unordered_multimap::bucket_size() Function
The C++ std::unordered_multimap::bucket_size() function is used to returns the number of elements presents in the nth bucket. A bucket is a slot in the container's internal hash table to which elements are assigned based on the hash value of their key. It has a range from 0 to bucket_count - 1.
Syntax
Following is the syntax of std::unordered_multimap::bucket_size().
size_type bucket_size(size_type n) const;
Parameters
- n − It indicates the bucket number that should be lower than bucket_count.
Return value
This function returns the total number of elements from current bucket.
Example 1
In the following example, let's see the usage of unordered_multimap::bucket_size() function.
#include <iostream> #include <unordered_map> using namespace std; int main(void) { unordered_multimap<char, int> umm = { {'a', 1}, {'b', 2}, {'c', 3}, {'d', 4}, {'e', 5} }; for (int i = 0; i < umm.bucket_count(); ++i) cout << "Bucket " << i << " contains "<< umm.bucket_size(i) << " elements." << endl; return 0; }
Output
If we run the above code it will generate the following output −
Bucket 0 contains 2 elements. Bucket 1 contains 2 elements. Bucket 2 contains 0 elements. Bucket 3 contains 0 elements. Bucket 4 contains 0 elements. Bucket 5 contains 0 elements. Bucket 6 contains 2 elements.
Example 2
Consider the following example, where we are going to use the bucket_size() function to get the count of elements present in each bucket.
#include <iostream> #include <unordered_map> using namespace std; int main(void) { unordered_multimap<char, int> umm; umm.insert({ {'a', 10}, {'b', 20}, {'a', 10}, {'b', 30}, {'c', 40} }); for (int i = 0; i < umm.bucket_count(); ++i) cout << "Bucket " << i << " contains "<< umm.bucket_size(i) << " elements." << endl; return 0; }
Output
Following is the output of the above code −
Bucket 0 contains 0 elements. Bucket 1 contains 0 elements. Bucket 2 contains 0 elements. Bucket 3 contains 0 elements. Bucket 4 contains 0 elements. Bucket 5 contains 0 elements. Bucket 6 contains 2 elements. Bucket 7 contains 2 elements. Bucket 8 contains 1 elements. Bucket 9 contains 0 elements. Bucket 10 contains 0 elements. Bucket 11 contains 0 elements. Bucket 12 contains 0 elements.
Example 3
Let's look at the following example, where we are going to use the bucket_size() function.
#include <iostream> #include <unordered_map> using namespace std; int main(void) { unordered_multimap<char, int> umm; umm.insert({ {'a', 10}, {'b', 20}, {'a', 10}, {'b', 30}, {'c', 40} }); for (int i = 0; i < umm.bucket_count(); ++i){ if(i%2!=0){ cout << "Bucket " << i << " contains "<< umm.bucket_size(i) << " elements." << endl; } } return 0; }
Output
Output of the above code is as follows −
Bucket 1 contains 0 elements. Bucket 3 contains 0 elements. Bucket 5 contains 0 elements. Bucket 7 contains 2 elements. Bucket 9 contains 0 elements. Bucket 11 contains 0 elements.