Set in C++ Standard Template Library (STL)

Sets are a type of associative containers in which each element has to be unique, because the value of the element identifies it. The value of the element cannot be modified once it is added to the set, though it is possible to remove and add the modified value of that element.

Some basic functions associated with Set:



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#include <iostream>
#include <set>
#include <iterator>
  
using namespace std;
  
int main()
{
    // empty set container
    set <int, greater <int> > gquiz1;        
  
    // insert elements in random order
    gquiz1.insert(40);
    gquiz1.insert(30);
    gquiz1.insert(60);
    gquiz1.insert(20);
    gquiz1.insert(50);
    gquiz1.insert(50); // only one 50 will be added to the set
    gquiz1.insert(10);
  
    // printing set gquiz1
    set <int, greater <int> > :: iterator itr;
    cout << "\nThe set gquiz1 is : ";
    for (itr = gquiz1.begin(); itr != gquiz1.end(); ++itr)
    {
        cout << '\t' << *itr;
    }
    cout << endl;
  
    // assigning the elements from gquiz1 to gquiz2
    set <int> gquiz2(gquiz1.begin(), gquiz1.end());
  
    // print all elements of the set gquiz2
    cout << "\nThe set gquiz2 after assign from gquiz1 is : ";
    for (itr = gquiz2.begin(); itr != gquiz2.end(); ++itr)
    {
        cout << '\t' << *itr;
    }
    cout << endl;
  
    // remove all elements up to 30 in gquiz2
    cout << "\ngquiz2 after removal of elements less than 30 : ";
    gquiz2.erase(gquiz2.begin(), gquiz2.find(30));
    for (itr = gquiz2.begin(); itr != gquiz2.end(); ++itr)
    {
        cout << '\t' << *itr;
    }
  
    // remove element with value 50 in gquiz2
    int num;
    num = gquiz2.erase (50);
    cout << "\ngquiz2.erase(50) : ";
    cout << num << " removed \t" ;
    for (itr = gquiz2.begin(); itr != gquiz2.end(); ++itr)
    {
        cout << '\t' << *itr;
    }
  
    cout << endl;
  
    //lower bound and upper bound for set gquiz1
    cout << "gquiz1.lower_bound(40) : "
         << *gquiz1.lower_bound(40) << endl;
    cout << "gquiz1.upper_bound(40) : "
         << *gquiz1.upper_bound(40) << endl;
  
    //lower bound and upper bound for set gquiz2
    cout << "gquiz2.lower_bound(40) : "
         << *gquiz2.lower_bound(40) << endl;
    cout << "gquiz2.upper_bound(40) : "
         << *gquiz2.upper_bound(40) << endl;
  
    return 0;
  
}
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The output of the above program is :

The set gquiz1 is :      60    50    40    30    20    10

The set gquiz2 after assign from gquiz1 is : 10      20    30    40    50    60

gquiz2 after removal of elements less than 30 : 30    40    50    60
gquiz2.erase(50) : 1 removed     30    40    60
gquiz1.lower_bound(40) : 40
gquiz1.upper_bound(40) : 30
gquiz2.lower_bound(40) : 40
gquiz2.upper_bound(40) : 60

Methods of set:

 
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