C++ - Sets & Unordered Sets

Overview

Estimated time: 40–60 minutes

Store unique elements with ordered std::set or hash-based std::unordered_set. Learn insertion, lookup, and iteration.

Learning Objectives

• Choose set vs unordered_set based on ordering vs average O(1) lookup.

Examples

#include 
#include 
#include 
int main(){
  std::set s; s.insert(3); s.insert(1);
  for (int x: s) std::cout << x << ' '; // 1 3
  std::unordered_set us; us.insert(5);
}

Common Pitfalls

• unordered_set has no stable iteration order; avoid depending on it.