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Why do people do this(graphs)?
By iamdumb, history, 9 years ago, In English

I have seen many time people starting dfs with starting node -1 but I don't understand why do they do this.Can you please tell me why do they do so like in this example.

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9 years ago, # |
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It's not starting point, it's a parent of verticle in DFS's spannig tree. There is no parent of root of the spanning tree, so it's equal to -1

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