Pseudo Code

Lesson 4 of 9 in Coddy's Bellman-Ford Algorithm - Graph Algorithms course.

bellmanFord(n, edges, source):
   dist = [INF, INF, ...]; dist[source] = 0
   repeat (n - 1) times:
      for each edge (u -> v, weight w):
         if dist[u] != INF and dist[u] + w < dist[v]:
            dist[v] = dist[u] + w
   replace every remaining INF with -1
   return dist

// negative cycle: after n-1 passes, if any edge STILL relaxes, a
// negative cycle exists.

The guard dist[u] != INF stops us from building paths out of unreachable vertices.
Relaxing the whole edge list is one pass. Bellman-Ford is just that pass repeated n - 1 times.

Try it yourself

This lesson doesn't include a code challenge.