C++: What is the STL?

STL (Standard Template Library) — collection of template classes and functions.

Components:

1. Containers:

• vector — dynamic array.
• list — doubly linked list.
• deque — double-ended queue.
• array — fixed-size array.
• forward_list — singly linked list.
• set — sorted unique elements.
• map — sorted key-value pairs.
• unordered_set — hash set.
• unordered_map — hash map.
• stack, queue, priority_queue.

2. Algorithms:

• sort, find, binary_search.
• transform, accumulate.
• copy, fill, remove.

3. Iterators:

• Input, output, forward, bidirectional, random access.

4. Function objects (functors):

• less, greater, plus, negate.

Example:

1#include <vector>
2#include <algorithm>
3
4std::vector<int> v = {3, 1, 4, 1, 5};
5
6// Sort
7std::sort(v.begin(), v.end());
8
9// Find
10auto it = std::find(v.begin(), v.end(), 4);
11
12// Transform
13std::transform(v.begin(), v.end(), v.begin(),
14    [](int x) { return x * 2; });