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GATE 2021 CS (CS2) – Question 11

Algorithms · Graph Algorithms: Traversals, Minimum Spanning Trees, Shortest Paths · 1 mark · Multiple choice

G is connected, undirected and weighted. S1: Some minimum-weight edge of G is present in every MST. S2: If all edge weights are distinct, G has a unique MST. Which are true?

  1. Both
  2. S1 true,S2 false
  3. S1 false,S2 true
  4. Neither

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Show answer and explanation

Correct answer: (C) S1 false,S2 true

Explanation

S1 fails for a triangle with all equal weights: each edge is minimum, but each can be omitted by some MST. S2 is the distinct-weight uniqueness theorem, following from the cut/exchange property. Thus S1 is false and S2 true, C.

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