Summary - STL containers
- C++ course
- Intermediate
- Lesson 58/116
- 5 min
Combine vector, map and set to write a phone book.
Summary - STL containers
In this group you learned five core STL containers. std::vector is a dynamic array, std::list a doubly linked list, std::map an ordered key-value store, std::unordered_map a hash table, std::set a unique sorted set.
In the final task you'll combine vector and set: create a vector with duplicate elements, then build a set from it. The set ignores duplicates, so its size gives the unique count. This is a common container-composition pattern.
Practice Mini task: combine vector and set
Create std::vector<int> v;; add 1, 2, 2, 3 with push_back. Build std::set<int> s(v.begin(), v.end());. Print s.size().
Starter code
#include <iostream>
#include <vector>
#include <set>
// add 1, 2, 2, 3 to a vector
// create a set from the vector
int main() {
// print the set size
return 0;
}Sample solution
#include <iostream>
#include <vector>
#include <set>
int main() {
std::vector<int> v;
v.push_back(1);
v.push_back(2);
v.push_back(2);
v.push_back(3);
std::set<int> s(v.begin(), v.end());
std::cout << s.size() << std::endl;
return 0;
}Expected output
3
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Which container for fast O(1) access when order doesn't matter?
// anahtar-değer, sıralama önemli değil- std::map
- std::set
- std::list
- std::unordered_map Correct answer
Explanation: unordered_map offers average O(1) access; no ordering.
2 Match container to property
| Term | Meaning |
|---|---|
std::vector |
Dynamic array |
std::list |
Doubly linked list |
std::map |
Ordered key-value |
std::set |
Unique sorted |
3 Key-value container
std::____<std::string, int> m;std::map<std::string, int> m;Explanation: std::map<std::string, int> m; is an ordered key-value container.