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
#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