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Reference's blog

By Reference, history, 8 years ago, In English

in bellman ford algorithm when i relax an edge(u,v) but the distance in u and v is infinite dist[u] = dist[v] = oo and the weight of edge is big negative so what will happen is: dist[u]+w < dist[v] so dist[v] will modified i want to asked if there is necessity to write a condition before the relaxing to avoid that or not and why if not ? because i try some graphs with an arbitary order to edges it gives wrong answer without the condition. thank you all.

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8 years ago, # |
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At least use commas...

You will need to check for negative cycles, rather than edges with negative weights.
To do that, iterate through the E edges again (After Bellman-Ford) and see if any vertex is still "relaxable". If so, there exists at least 1 negative cycle on the graph which means there are no shortest paths for certain vertices.