HASHSET IN C++

The C++ std::unordered_set is a container provided by the C++ Standard Library that stores a collection of unique elements. It is based on a hash table data structure and allows for fast insertion, removal, and lookup of elements. Here’s how you can use std::unordered_set:

#include <iostream>
#include <unordered_set>

int main() {
    // Declare an unordered_set of integers
    std::unordered_set<int> mySet;

    // Insert elements into the unordered_set
    mySet.insert(10);
    mySet.insert(20);
    mySet.insert(30);

    // Check if an element exists in the unordered_set
    if (mySet.find(20) != mySet.end()) {
        std::cout << "Element 20 is in the set." << std::endl;
    } else {
        std::cout << "Element 20 is not in the set." << std::endl;
    }

    // Iterate through the unordered_set
    for (int element : mySet) {
        std::cout << element << " ";
    }
    std::cout << std::endl;

    // Remove an element from the unordered_set
    mySet.erase(20);

    // Check the size of the unordered_set
    std::cout << "Size of the set: " << mySet.size() << std::endl;

    return 0;
}

In this example:

• We include the necessary headers, <iostream> and <unordered_set>.
• We declare an std::unordered_set called mySet to store integers.
• We insert elements into the unordered_set using the insert method.
• We check if an element exists in the unordered_set using the find method.
• We iterate through the unordered_set using a range-based for loop.
• We remove an element from the unordered_set using the erase method.
• We check the size of the unordered_set using the size method.

std::unordered_set is a useful container when you need to store a collection of unique elements and perform fast insertion, removal, and lookup operations. The order of elements in an std::unordered_set is not guaranteed to be in any particular order; it depends on the hash function and the underlying implementation.