set unordered_set

unordered_set is a container in C++ Standard Template Library (STL) that stores a collection of unique elements. It is an associative container, meaning the elements are stored using a hash table implementation to provide constant-time average complexity for insertion, deletion, and search operations.

To use unordered_set in C++, you need to include the <unordered_set> header file and declare a variable of type unordered_set. Here's an example:

#include <unordered_set>

int main() {
  std::unordered_set<int> set;

  // Insert elements
  set.insert(10);
  set.insert(20);
  set.insert(30);

  // Check if an element exists
  if (set.find(20) != set.end()) {
    std::cout << "Element found!" << std::endl;
  }

  // Remove an element
  set.erase(10);

  return 0;
}

In this example, we create an unordered_set called `set` to store integers. We insert three elements (10, 20, and 30) using the `insert` function. We then check if the element 20 exists using the `find` function and erase the element 10 using the `erase` function.