Concepts4

Constructive algorithms build a valid answer directly by following a recipe, rather than searching exhaustively.

Tree isomorphism asks whether two trees have exactly the same shape, ignoring vertex names.

A binary trie (also called a bitwise trie) stores numbers by their binary bits, branching on 0/1 at each level.

std::set and std::map store elements in sorted order using a balanced binary search tree (typically a Red-Black Tree).