solmidterm2Sol

solmidterm2Sol - Solution to Midterm 2 Fall 2008 cs170...

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Solution to Midterm 2 Fall 2008 cs170 Problem 1 [60 points] 1. 0.55 0.3 0.1 0.05 2. True 3. 3 1 1 4. -5 20 22 Dijkstra outputs (S,A) and (S,B) as the final tree with shortest path distances of 20 , and 22 respectively. In Dijkstra algorithm once a node is removed from the priority queue, it means that its shortest distance is finalized and other nodes cannot update it. Therefore since A is removed before B then the updates of B do not have any effect on A . Here is how the priority queue works: Initially there are A(0), B( ∞ ), A(∞ ) on the queue. Then A is removed and B( ∞ ) , A( ∞ ) are updated to B(22), A(20) . Now A is removed from the priority queue and since it does not have any children no updates are done. The value of A so far is 20 and it is not going to change because A is removed from our priority queue. Finally B is removed from the priority queue, but there are no nodes to update are removed from our priority queue.
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This note was uploaded on 04/30/2010 for the course L&S 101 taught by Professor Chow during the Spring '10 term at Berkeley.

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solmidterm2Sol - Solution to Midterm 2 Fall 2008 cs170...

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