Set STL in CPP 👨‍🎓

Introduction

Set is a data structure that only stores unique elements.

Types of Set

There are two types of set in cpp.

1. Ordered Set - Maintain sorting while insertion
2. Unordered Set - Insert in random order which makes it fast.

Initialize

#include <set>
using namespace std;
int main(){
    set<int> iSet;
    unordered_set<int> uSet;
    iSet.insert(10);
    uSet.insert(10);
}

Check for an element

if (iSet.find(20) != iSet.end()) {
    cout << "20 is in the set" << endl;
}
if (uSet.find(20) != uSet.end()) {
    cout << "20 is in the set" << endl;
}

Erase an element

iSet.erase(20);
uSet.erase(20);

Iterate over an element

Iteration is same in ordered and Unordered Set

for (auto it = iSet.begin(); it != iSet.end(); ++it) {
    std::cout << *it << " ";
}

Get the size

std::cout << "Size: " << iSet.size() << std::endl;
std::cout << "Unordered Size: " << uSet.size() << std::endl;

Clear the set

iSet.clear();

Difference Between Ordered and Unordered set

Feature	std::set	std::unordered_set
Order	Stores elements in sorted order	No particular order
Time Complexity	O(log n) for insert, delete, search	O(1) average for insert, delete, search
Duplicates	Not allowed	Not allowed
Use Case	When sorting is needed	When fast operations are needed

Application

1. Removing duplicates in an array
2. Set Operations