The Standard Template Library
The Standard Template Library offers a lot of ready-to-use implementations of the most common data structures and algorithms. It contains implementations of basically all containers you will ever need, as well as the Algorithms library for manipulating containers.
A small selection of algorithms:
find: Finds and element in a range.sort: Sorts a range of elements.transform: Applies a function to a range of elementsbinary_search: Performs a binary search on a sorted range.
Have a look at the C++ reference for a list of all available containers and algorithms.