unordered set of Vectors in C++ with Examples

How to Store Duplicate Elements in Ordered Set in C++?

Last Updated : 03 Dec, 2024

The ordered set is a policy-based data structure in GNU C++ that contains unique elements in sorted order just like set. In this article, we will learn how to store duplicates in ordered set.

To store duplicates in an ordered set, use a pair data type where the first value of the pair will store the element, and the second value will store some other unique information like index or even some random number. Let's take a look at an example:

C++

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;

// Declaring ordered_set for pair<int,int>
typedef tree<pair<int, int>, null_type, 
less<pair<int, int>>, rb_tree_tag, 
tree_order_statistics_node_update> os;

int main() {
    vector<int> v = {1, 2, 2, 1, 3};
  
  	// Creating ordered set
    os s;

    // Inserting duplicate elements in 
    // ordered set
    for (int i = 0; i < v.size(); i++)
        s.insert({v[i], i});

    for (auto i : s)
        cout << i.first << " ";
    return 0;
}

Output

1 1 2 2 3

Explanation: In the above code, storing duplicate elements in an ordered set pair with a unique second value will make the pair different from one another.

unordered set of Vectors in C++ with Examples

S

sachin801

Improve

Article Tags :

Practice Tags :

Similar Reads

How to Insert a Range of Elements in a Set in C++ STL?

Prerequisites: Set in C++ Sets in C++ are a type of associative container in which each element has to be unique because the value of the element identifies it. The values are stored in a specific sorted order i.e. either ascending or descending. Syntax: set<datatype> set_name; Some Basic Func

How to Erase Duplicates and Sort a Vector in C++?

In this article, we will learn how to remove duplicates and sort a vector in C++.The simplest method to remove the duplicates and sort the vector is by using sort() and unique() functions. Letâ€™s take a look at an example:C++#include <bits/stdc++.h> using namespace std; int main() { vector<i

unordered_set emplace_hint() function in C++ STL

The unordered_set::emplace_hint() function is an inbuilt function in C++ STL which inserts a new element in the unordered_set only if the value to be inserted is unique, with a given hint. Syntax: unordered_set_name.emplace_hint( position, value ) Parameter: This function accepts two parameters as m

unordered set of Vectors in C++ with Examples

What is an unordered set? In C++, an unordered set is an unordered container that can hold a number of unique elements. Unlike a set, elements in an unordered set are not arranged in any particular order. Internally, an unordered set is implemented using a hash table where keys are hashed into indic

unordered_set insert() function in C++ STL

The unordered_set::insert() is a built-in function in C++ STL which is used to insert a new {element} in the unordered_set container. Each element is inserted only if it is not already present in the container (elements in an unordered_set have unique values). The insertion is done automatically at

How to Declare Comparator For Set of Pair in C++?

Prerequisites: Set in C++Pair in C++The set in STL has the property that it stores only the distinct values in the sorted order if the datatype is an integer, in lexicographically smallest to largest if the data type is a string. If the datatype is pair the set keeps the distinct pairs only with the