Consider a weighted undirected graph with positive edge weights and let (u, v)…

2012

Consider a weighted undirected graph with positive edge weights and let (u, v) be an edge in the graph. It is known that the shortest path from source vertex s to u has weight 53 and shortest path from s to v has weight 65. Which statement is always true?

  1. A.

    Weight (u, v) < 12

  2. B.

    Weight (u, v) = 12

  3. C.

    Weight (u, v) > 12

  4. D.

    Weight (u, v) ≥ 12

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Correct answer: D

In a weighted undirected graph, shortest path distances satisfy the triangle inequality. Since the shortest path to v is 65 and via u it would be at least 53 plus the edge weight, we have 65 ≤ 53 + w(u,v). Rearranging gives w(u,v) ≥ 12.

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