C++ Sets

C++ Sets: Unique and Sorted

In C++, a Set is a container that holds a collection of unique elements.

Sets have two very special rules:

1. No Duplicates: If you try to add an item that already exists in the set, the set ignores it.
2. Automatically Sorted: A standard C++ set will automatically sort its elements in ascending order as you add them!

1. Creating and Using a Set

Include the <set> library to use this data structure.

Because elements in a set are constantly shifting to stay sorted, you cannot access them via an index (like mySet[0]).

#include <iostream>
#include <set>
using namespace std;

int main() {
  // Create a set of integers
  set<int> mySet;
  // Insert elements
  mySet.insert(50);
  mySet.insert(10);
  mySet.insert(30);
  // Try to insert a duplicate!
  mySet.insert(10); 
  // Iterate through the set (Notice it's sorted automatically!)
  for (int num : mySet) {
    cout << num << " "; // Output: 10 30 50
  }
  cout << "\nTotal unique elements: " << mySet.size() << "\n";
  return 0;
}

2. Fast Searching with Sets

Under the hood, C++ sets are typically implemented as Binary Search Trees. This makes finding data incredibly fast. You can check if an item exists in the set using the .count() method (which returns 1 if it exists, and 0 if it doesn't).