Searching Algorithms (find, binary_search, lower_bound)

The <algorithm> header provides two families of search functions: linear scans that work on any sequence, and binary searches that require a sorted range. Picking the wrong family is one of the common STL mistakes: calling std::binary_search on an unsorted vector compiles, runs, and returns wrong answers. This chapter walks through both families, the iterator categories they expect, the rules around custom comparators, and the classic "I need the position, not a yes/no answer" pitfall.