A concise Swift 2.2 implementation of Dave Thomas's Transitive Dependencies programming exercise, also known as a kata.
My approach to solving this problem involves visiting nodes in a dependency graph by iterating through a node's direct dependencies, recursing into indirect dependencies if possible. A Set collection is used to accumulate dependencies when applying reduce to a node's direct dependencies. That Set is also used to check if a node has already been visited, to avoid navigating cyclical dependencies.
Check out the details in main.swift.