Implement Prototype(n int,edges [][3]int) ([][]*int,error) by Bellman–Ford from each source; Solve uses Floyd–Warshall O(V³) time and O(V²) memory. Directed signed edges; keep cheapest parallel edge. Return n×n distance matrix with nil unreachable and pointer zero diagonal if no negative cycle. n=0 returns nonnil empty. Error for negative n, invalid endpoints, or any negative cycle. Preserve input.
Edit exercise.go; retain the public types and signatures. prototype and final are separate stages. The executable tests recover panics as failures, report named checks, and exit nonzero on any failure. A successful run must execute at least one check. Tests use logical time or explicit synchronization where relevant.
Complete the starter code, then run the checks.
Results and errors will appear here.