C++ defines a set of generic algorithms such as sort and find. However, the corresponding C algorithms, qsort and bsearch, are still useful in C++ programs for at least three reasons:
- Legacy code. Familiarity with C algorithms is needed to maintain legacy C code.
- Efficiency. You cannot apply STL algorithms to items that are not stored in an STL container. To apply these algorithms to a built-in array, you first have to copy it into a container–an operation that incurs runtime overhead.
- Applicability to non-OO data types. STL algorithms rely on operators == and >. However, these operators are either meaningless or not defined when applied to plain structs or built-in arrays. C algorithms do not rely on these operators to work.
