C++ Set Library - set() Function

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Description

The C++ constructor std::set::set() constructs an empty set container with no elements in it.

Declaration

Following is the declaration for std::set::set() constructor form std::set header.

C++98

explicit set(const key_compare& comp = key_compare(),
             const allocator_type& alloc = allocator_type());

C++11

explicit set(const key_compare& comp = key_compare(),
             const allocator_type& alloc = allocator_type());
explicit set(const allocator_type& alloc);

C++14

set();
explicit set(const key_compare& comp,
             const allocator_type& alloc = allocator_type());
explicit set(const allocator_type& alloc);

Parameters

• alloc − Input iterator to initial position.

• comp − comparison function object to use for all comparisons of keys

Return value

Constructor never returns any value.

Exceptions

This member function has no effect in case any exception is thrown.

Time complexity

Constant i.e. O(1)

Example

The following example shows the usage of std::set::set() constructor.

#include <iostream>
#include <set>

using namespace std;

int main(void) {
   // Default constructor
   std::set<char> t_set;
  
   t_set.insert('a');
   t_set.insert('e');
   t_set.insert('i');
   t_set.insert('o');
   t_set.insert('u');
  
   int size = t_set.size(); 

   std::cout << "Contents of set container t_set = " << size;
   return 0;
}

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

Contents of set container t_set = 5