C++

STL Containers & Algorithms

Templates are what make this possible: the Standard Template Library (STL) is a set of ready-made, templated data structures and algorithms — a resizable array, a key-value map, sorting, searching — that would otherwise be exactly the kind of code the Embedded C domain shows you how to hand-roll from scratch, this time already written, tested, and generic over whatever type you need.

Quick reference
What it is
A collection of template classes (containers) and template functions (algorithms) forming C++'s standard data-structure toolkit.
Mental model
A well-stocked toolbox that ships with the language — before reaching for a hand-rolled linked list or array, check whether the STL already has exactly the tool you need.
Key numbers
std::vector is the default "just give me a resizable array" choice in the overwhelming majority of real C++ code — reach for anything else only when you have a specific reason to.
Reach for it when
Almost always, on a target with enough memory to afford it — the STL is heavily used, well-tested, and removes real, repeated boilerplate versus hand-rolling equivalents.

std::vector

std::vector is a dynamically-resizable array — the direct, safer upgrade from C's fixed-size arrays, growing automatically as elements are added: 

#include <vector>

std::vector<int> readings;
readings.push_back(23);
readings.push_back(45);
readings.push_back(12);

std::cout << readings.size() << std::endl;   // 3 — tracked automatically
std::cout << readings[1] << std::endl;        // 45 — indexing works just like a C array

Unlike a C array, readings.size() is always known — no separate length variable to keep in sync by hand, and no risk of the array/length pair drifting out of sync, a real recurring source of bugs in equivalent C code.

Other common containers

ContainerWhat it isReach for it when
std::vectorDynamically-resizable arrayThe default choice — fast indexed access, grows as needed
std::mapSorted key-value pairsLooking values up by a key, and iteration order (sorted by key) matters
std::unordered_mapHash-table key-value pairsLooking values up by a key, and order doesn't matter — faster lookup than map
std::setSorted, unique valuesNeeding a collection with no duplicates, automatically sorted
std::queueFirst-in-first-outThe STL version of C's hand-rolled queues
 
#include <map>

std::map<std::string, float> sensorReadings;
sensorReadings["temperature"] = 23.5f;
sensorReadings["humidity"] = 45.0f;

std::cout << sensorReadings["temperature"] << std::endl;   // 23.5 — looked up by name, not by index

The algorithms library

<algorithm> provides generic, templated functions that work across every STL container — sorting, searching, and transforming, without writing the loop by hand: 

#include <algorithm>
#include <vector>

std::vector<int> readings = {45, 12, 78, 23, 5};

std::sort(readings.begin(), readings.end());
// readings is now {5, 12, 23, 45, 78}

auto it = std::find(readings.begin(), readings.end(), 23);
if (it != readings.end()) {
    std::cout << "Found 23\n";
}

begin()/end() are iterators — a generic "position within a container" concept every STL container provides, letting the same std::sort function work identically across a vector, a set, or any other compatible container without being rewritten per container type.

Range-based for loops

A cleaner alternative to the index-based C-style for loop when you just need every element, in order, without caring about the index itself: 

for (int reading : readings) {
    std::cout << reading << std::endl;   // no index variable, no bounds to get wrong
}

Real-world applications

Gotchas

Field notes