When Floyd-Warshall Wins

Floyd-Warshall computes distances between every pair of nodes in $O(N^3)$. Use it when N ≤ $400$ and you need all-pairs distances. If N = $1000$, $O(N^3) = 10^9$ operations.

Too slow. Run Dijkstra N times instead if weights are non-negative. Floyd-Warshall also works with negative edges and detects negative cycles. Check the diagonal after running it: if dist[i][i] < 0 for any $i$, a negative cycle exists that passes through node $i$.