GATE CS 2021 Set 2 — Question 65
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Question
In a directed acyclic graph with a source vertex , the quality-score of a directed path is defined to be the product of the weights of the edges on the path. Further, for a vertex other than , the quality-score of is defined to be the maximum among the quality-scores of all the paths from to . The quality-score of is assumed to be 1.
The sum of the quality-scores of all the vertices in the graph shown above is __________.

Correct answer
929 to 929
Solution
Let denote the quality-score of vertex . We are given .
For any other vertex , .
This can be computed using dynamic programming or by processing vertices in topological order: .Let's compute the quality-scores for each vertex:
Sum
Sum
Sum
Sum
Sum .
For any other vertex , .
This can be computed using dynamic programming or by processing vertices in topological order: .Let's compute the quality-scores for each vertex:
1.: (Given)
2.: Incoming from . .
3.: Incoming from . .
4.: Incoming from . .
5.: Incoming from . .
6.: Incoming from and .
- Via :
- Via :
- .
- Via :
- Via :
- .
- Via :
- Via :
- .
- Via :
- Via :
- .
Sum
Sum
Sum
Sum
Sum .
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