C++ Unordered_set::cend() Function

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TheC++std::unordered_set::cend() function is used to return a const_iterator pointing to the past-the-last element in the unordered_set container. The const_iterator returned by the cend does not point to any element but the position followed by the last element in the unordered_set container.

In STL CPP, a const_iterator is an iterator that points to a const value (like a pointer) over elements and provides access to each individual element. const_terators are not allowed to modify pointed elements available in the unordered_set container.

The unordered_set::cend() function is similar to the unordered_set::end() function. The cend() function returns only a const_iterator, whereas the end() function returns only an iterator.

Syntax

Following is the syntax of std::unordered_set::cend() function.

const_iterator cend() const noexcept;
or
const_local_iterator cend ( size_type n ) const;

Parameters

• n − It indicates the bucket number that must be less than the bucket_count.

Return Value

This function returns a const_iterator pointing to the position followed by the last element in the unordered_set container.

Example 1

Let's look at the following example, where we are going to use the loop to display the element of the container in a range.

#include <iostream>
#include <string>
#include <unordered_set>

int main () {
   std::unordered_set<std::string> myUset =
      {"100","200","300","400","500"};
      
   std::cout << "myUset contains:";
   for ( auto it = myUset.cbegin(); it != myUset.cend(); ++it )
      std::cout << " " << *it;
   std::cout << std::endl;
   
   return 0;
}

Output

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

myUset contains: 500 400 300 200 100

Example 2

Consider the following example, where we are going to use the cend() function that accepts i as parameter to return the elements of each bucket.

#include <iostream>
#include <string>
#include <unordered_set>

int main () {
   std::unordered_set<std::string> myUset = {"100", "200", "300", "400", "500"};
      
   std::cout << "myUset's buckets contain:\n";
   for ( unsigned i = 0; i < myUset.bucket_count(); ++i) {
      std::cout << "bucket #" << i << " contains:";
      for ( auto local_it = myUset.cbegin(i); local_it!= myUset.cend(i); ++local_it )
         std::cout << " " << *local_it;
      std::cout << std::endl;
   }
   return 0;
}

Output

If we run the above code it will generate the following output −

myUset's buckets contain:
bucket #0 contains:
bucket #1 contains: 400
bucket #2 contains: 500
bucket #3 contains:
bucket #4 contains: 100
bucket #5 contains:
bucket #6 contains:
bucket #7 contains:
bucket #8 contains:
bucket #9 contains:
bucket #10 contains: 300
bucket #11 contains: 200
bucket #12 contains:

Example 3

In the following example, we are going to use the cend() function to get the elements of the unordered_set container by iterating over the unordered_set using the while loop.

#include <iostream>
#include <unordered_set>  
#include <string> 
using namespace std;
 
int main() {
   unordered_set<int> myset = { 10,20,30,40,50 };  
      cout<<"Elements of myUset are: "<<endl;  
   unordered_set<int>::const_iterator it; // declare an iterator 
   it = myset.begin();
   while (it != myset.cend()) {  
      cout << *it << "\n"; 
      ++it; // iterate to the next element  
   }  
   cout << endl;  
   return 0;
} 

Output

Following is the output of the above code −

Elements of myUset are: 
50
40
30
20
10