Implement a hierarchical key-value store

# Solution Alignment The prompt asks for an implementation-level answer. The safest way to present it is to define the state, maintain clear invariants, then walk through complexity and tests. ## Problem Restatement Implement an in-memory hierarchical key-value store where keys are UNIX-like paths joined by '/'. The root node is '/' with initial value '#'. Each node stores a string value. Support: ( 1) Create(path, value): create a node; parent must exist; fail if the node already exists. ( 2) SetValue(path, value): set the value; node must exist. ( 3) GetValue(path): return the value; node must exist. ( 4) Delete(path): delete the node only if it has no children; node must exist. Define the class interface, choose appropriate data structures, and provide time/space complexities. Include unit tests and discuss how you would add concurrency safety and optional persistence to disk. ## Recommended Approach Model the states explicitly and use BFS for unweighted shortest paths, Dijkstra for weighted non-negative paths, or topological DP for DAGs. Track visited states at the right granularity so cycles do not cause repeated work. ## Correctness The implementation should maintain an invariant after each loop or operation that directly matches the problem statement. At termination, that invariant implies the returned value has considered every valid candidate exactly once, or has preserved the required data-structure state after every API call. ## Complexity BFS is O(V + E) time and O(V) space for a standard graph. Expanded-state problems multiply those bounds by the number of state dimensions. ## Edge Cases and Tests Disconnected graph, source equals target, cycles, duplicate edges, unreachable target, and whether the answer counts nodes, edges, moves, or transfers.