Is it true that the heaviest edge in a directed graph can not be in the MST of that graph?

I don't think it is true because we might end up with a heaviest edge that is not part of a cycle.

Can anyone confirm?

  • 1
    $\begingroup$ Let $G$ be a graph with a bridge. $\endgroup$
    – Pål GD
    May 9, 2013 at 15:24

1 Answer 1


No, it is not true. Consider a graph with 2 vertices and an edge between them. This is the heaviest edge, and it will be in the minimum spanning tree of $G$.

  • 2
    $\begingroup$ And this is not degenerate example, a leaf node with the heaviest edge... $\endgroup$
    – Aryabhata
    May 9, 2013 at 4:03
  • $\begingroup$ Yeah, consider any pendant vertex. $\endgroup$
    – Juho
    May 9, 2013 at 4:05
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    $\begingroup$ Or any edge in a tree. $\endgroup$ May 9, 2013 at 4:06
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    $\begingroup$ More precisely: the heaviest edge is not chosen iff it is on a cycle. $\endgroup$ May 9, 2013 at 7:33
  • 1
    $\begingroup$ Every bridge is in every MST. $\endgroup$
    – Pål GD
    May 9, 2013 at 15:23

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