Ordered Set and GNU C++ PBDS

In this tutorial, we will be discussing a program to understand ordered set and GNU C++ PBDS.

Ordered set is a policy based structure other than those in the STL library. The ordered set keeps all the elements in a sorted order and doesn’t allow duplicate values.

Example

 Live Demo

#include <iostream>
using namespace std;
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
#define ordered_set tree<int, null_type,less<int>, 
rb_tree_tag,tree_order_statistics_node_update>
int main(){
   //declaring ordered set
   ordered_set o_set;
   o_set.insert(5);
   o_set.insert(1);
   o_set.insert(2);
   cout << *(o_set.find_by_order(1))
      << endl;
   cout << o_set.order_of_key(4)
      << endl;
   cout << o_set.order_of_key(5)
      << endl;
   if (o_set.find(2) != o_set.end())
      o_set.erase(o_set.find(2));
   cout << *(o_set.find_by_order(1))
      << endl;
   cout << o_set.order_of_key(4)
      << endl;
   return 0;
}

Output

2
2
2
5
1