C++ Algorithms and Ranges

C++ Algorithms and Ranges

Classic STL algorithms, numeric algorithms, projections, iterators, and modern range views in one focused reference.

How to use this reference page

Use reference pages to confirm names, categories, nearby facilities, and the constraints that matter before writing or reviewing code.

Scan the top of the page first to identify the primary types, functions, or algorithm families involved.
Use the nearby-page links when your question is really about a companion header, related algorithm family, or broader subsystem.
Validate tricky behavior with a small compileable example before relying on memory for details like invalidation, ordering, allocation, or lifetime rules.

C++ Algorithms and Ranges

Classic algorithm families from `<algorithm>`

searching: find, find_if, binary_search, lower_bound, upper_bound
sorting and ordering: sort, stable_sort, partial_sort, nth_element
partitioning: partition, stable_partition
modification: copy, move, transform, replace, fill, remove, unique
set and heap operations: set_union, set_intersection, make_heap, push_heap, pop_heap

Numeric algorithms from `<numeric>`

accumulate
reduce
transform_reduce
inclusive/exclusive scans
adjacent_difference
gcd, lcm

Iterator and projection concepts

iterators are the original abstraction behind algorithms
ranges algorithms accept the range directly
projections let you sort or search by a member without a custom comparator body

std::ranges::sort(users, std::greater<>{}, &User::score);

Common view adaptors from `<ranges>`

filter
transform
take
drop
split
keys
values

Rules that matter in practice

prefer algorithms over handwritten loops when they communicate intent more clearly
keep predicates pure unless mutation is part of the algorithm contract
remember that views are lazy and usually borrowed
materialize into a container when you need stable ownership or multiple traversals over transient input

Example in practice

#include <ranges>
#include <vector>

int main() {
    std::vector<int> values{1, 2, 3, 4};
    auto even = values | std::views::filter([](int value) { return value % 2 == 0; });
    return *even.begin();
}