## NPTEL Artificial Intelligence : Search Methods For Problem solving Week 9 Assignment Answers 2024

1. Which of the following are mutex action pairs in Layer 1?

- Putdown(B), Stack(B,A)
- Putdown(B), Stack(B,D)
- Putdown(B), nop-4
- Putdown(B), nop-6

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2. Which of the following are mutex proposition pairs in Layer 1?

- holding(B), armEmpty
- on(D,C), armEmpty
- onTable(D), on(B,A)
- holding(B), clear(A)

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3. Which of the following are applicable actions in Layer 2?

- Pickup(B)
- Unstack(A,E)
- Unstack(B,A)
- Stack(B,D)

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4. Mutex relation in a planning graph ** ______________** .

- contains all possible mutex conditions that occur in a given problem
- grows monotonically as we move from layer k to layer k+1, for all k
- describes all action pairs that can be executed in parallel
- None of the above

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5. Select the correct statement about GraphPlan.

- It will find a plan if one exists.
- In some cases it may not find a plan even when a plan exists.
- It always returns an optimal plan if such a plan exists.
- It may not always return an optimal plan.
- Length of the plan depends on the ordering of the subgoals

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6. GraphPlan terminates ** ________________** .

- when the goal becomes true in a proposition layer.
- when two consecutive layers have the same set of propositions.
- when two consecutive layers have the same set of mutual exclusions.
- when two consecutive layers have the same set of propositions and the same set of mutual exclusions.

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7. The AO* algorithm, in each iteration, ** _______________** .

- expands the lowest-cost decomposition
- expands the highest-cost decomposition
- sometimes expands the lowest-cost decomposition and other times expands the highest-cost decomposition
- does not pay attention to the cost of the decomposition

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8. In AO* algorithm, ** _______________** .

- the children of OR node can be expanded in any order
- the lowest-cost child of OR node is expanded first
- the highest-cost child of OR node is expanded first

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9. In AO* algorithm, ** __** .

- the children of AND node can be expanded in any order
- the lowest-cost child of AND node is expanded first
- the highest-cost child of AND node is expanded first

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10. An AND-OR graph is a graph where ** _____________** .

- each node is a problem or a goal
- edges from nodes transform a problem into one or more simpler problems
- solved nodes stand for primitive problems that do not need further work
- the solution is always a path from the start node to a solved node

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11. In a AND-OR graph rooted at S, a node C (at some depth) has parents P, Q (at some depth). And P and C have been expanded in some order, and Q has been read but not expanded yet. During backward phase of AO* algorithm, when the cost of C is updated, that update may propagate to ** __** .

- Node P
- Node Q
- Root node S

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12. When is the root node S considered to be solved by the AO* algorithm?

- As soon as a leaf node is solved.
- As soon as a marked child of the start node is solved.
- As soon as one of the children of the start node is solved.
- When the start node retains the same value in two consecutive iterations.

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13. In the given AND-OR graph, how many full solutions (full decompositions) exist for the problem S? Count the number of full solutions.

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14. The first node expanded is S, what is the 2nd noded expanded by AO* algorithm?

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15. After the 2nd node is expanded, enter the cost of the 2nd node followed by the cost of node S as a comma separated list.

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16. Starting with S, list the nodes in the order they are expanded by AO* algorithm till it terminates. Observe that primitive nodes are not expanded. And use tie-breakers where needed.

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17. List the values of the start node S after every expansion listed above.

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18. What is the cost of the solution found by AO*?

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19. What is the solution found by AO*? List the nodes in the solution in ALPHABETICAL ORDER.

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20. Select the true statements

- AO* found the optimal solution.
- AO* did not find the optimal solution.
- Cannot be determined.

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