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May 2025 term · AI: Search Methods for Problem Solving · BSCS3003

AI: Search Methods for Problem Solving End Term: 31 August 2025, Set QDB1 (May 2025 term)

The IIT Madras BS AI: Search Methods for Problem Solving (AI Search Methods) End Term paper sat on 31 Aug 2025, in the May 2025 term, set QDB1: 28 questions for 27 marks in 180 minutes. Every question is below with its answer. Take it as a timed mock test to be marked, or read it through first.

Questions
28
Marks
27
Duration
180 min
MSQ
7
Written
14
MCQ
6
Numerical
1

Updated

Official paper: IIT M DIPLOMA AN EXAM QDD3 31 Aug 2025 · No negative marking.

Question 1

+0 marksOne or more correct options

Select all that apply.

  1. A

    Printed graph sheets were provided on time.

  2. B

    Printed graph sheets were provided late.

  3. C

    Printed graph sheets were not provided.

  4. D

    I used the graph sheets.

  5. E

    I did not use graph sheets.

Show answer

Correct answers

  • A

    Printed graph sheets were provided on time.

  • D

    I used the graph sheets.

Question 2

+1 markWritten answer

SEARCH

Based on the above data, answer the given subquestions.

What is the path found by the Best First Search algorithm? Enter the path as a comma separated list of node labels.
NO SPACES, TABS, DOTS, BRACKETS OR EXTRANEOUS CHARACTERS.
Answer format: S,X,Y,Z

Show answer

Correct answer: S,E,C,G

Question 3

+1 markWritten answer

SEARCH

Based on the above data, answer the given subquestions.

NO SPACES, TABS, DOTS, BRACKETS OR EXTRANEOUS CHARACTERS.
Answer format: S,X,Y,Z

Show answer

Correct answer: S,F,B,A,G

Question 4

+1 markWritten answer

SEARCH

Based on the above data, answer the given subquestions.

What is the path found by Branch-and-Bound search algorithm? Enter the path as a comma separated list of node labels.
Use the Branch-and-Bound variation that avoids cyclic expansions like S,E,S,E,S,E,...
NO SPACES, TABS, DOTS, BRACKETS OR EXTRANEOUS CHARACTERS.
Answer format: S,X,Y,Z

Show answer

Correct answer: S,F,B,A,G

Question 5

+1 markOne correct option

SEARCH

Based on the above data, answer the given subquestions.

For the given map, which algorithm finds the shortest path from S to G?

  1. A
  2. B
  3. C
  4. D
Show answer

Correct answer

  • C

Question 6

+1 markOne correct option

SEARCH

Based on the above data, answer the given subquestions.

Select the correct statement(s) about the given graph.

  1. A

    Heuristic is admissible.

  2. B

    Heuristic is not admissible.

  3. C

    Heuristic is admissible in some cases and not admissible in other cases.

  4. D

    There is not enough information to determine admissibility.

Show answer

Correct answer

  • A

    Heuristic is admissible.

Question 7

+1 markWritten answer

TSP Branch-and-Bound
The TSP Branch-and-Bound algorithm is solving a TSP instance where the cities are A, B, C, .... and so on. The Branch-and-Bound search tree at the time when the algorithm has discovered the optimal tour is shown below.
Each node in the search tree displays an edge (either XY or ~XY), a cost value, and a unique reference number (a1, b1, b2, ..., c1, ..., d1, ..., e1, e2). Use the reference numbers to break ties. When required, enter the reference numbers in short answers.
What information can you glean from the search tree? Answer the sub-questions based on the information gleaned from the search tree.

Let S0 (ref. no. a1) be the first node to be refined, identify the next 4 nodes (2nd to 5th node) that are refined by the TSP Branch-and-Bound algorithm. Enter the nodes (node reference numbers) in the order they are refined.
Enter a comma separated list of node reference numbers.
NO SPACES, TABS, DOTS, BRACKETS OR EXTRANEOUS CHARACTERS.
Answer format: a9,b9,c9,d9

Show answer

Correct answer: b1,c2,b2,c3

Question 8

+1 markWritten answer

TSP Branch-and-Bound
The TSP Branch-and-Bound algorithm is solving a TSP instance where the cities are A, B, C, .... and so on. The Branch-and-Bound search tree at the time when the algorithm has discovered the optimal tour is shown below.
Each node in the search tree displays an edge (either XY or ~XY), a cost value, and a unique reference number (a1, b1, b2, ..., c1, ..., d1, ..., e1, e2). Use the reference numbers to break ties. When required, enter the reference numbers in short answers.
What information can you glean from the search tree? Answer the sub-questions based on the information gleaned from the search tree.

Which node represents the optimal tour? Enter the node reference number in the text box, or enter NIL if it is not possible to determine the optimal tour.
Enter a node reference number.
NO SPACES, TABS, DOTS, BRACKETS OR EXTRANEOUS CHARACTERS.
Answer format: a9

Show answer

Correct answer: d3

Question 9

+1 markWritten answer

TSP Branch-and-Bound
The TSP Branch-and-Bound algorithm is solving a TSP instance where the cities are A, B, C, .... and so on. The Branch-and-Bound search tree at the time when the algorithm has discovered the optimal tour is shown below.
Each node in the search tree displays an edge (either XY or ~XY), a cost value, and a unique reference number (a1, b1, b2, ..., c1, ..., d1, ..., e1, e2). Use the reference numbers to break ties. When required, enter the reference numbers in short answers.
What information can you glean from the search tree? Answer the sub-questions based on the information gleaned from the search tree.

What is the cost of the optimal tour? Enter the cost of the optimal tour in the text box, or enter NIL if it is not possible to determine the optimal tour.
Enter an integer.
NO SPACES, TABS, BRACKETS OR EXTRANEOUS CHARACTERS.
Answer format: 42

Show answer

Correct answer: 434

Question 10

+1 markWritten answer

TSP Branch-and-Bound
The TSP Branch-and-Bound algorithm is solving a TSP instance where the cities are A, B, C, .... and so on. The Branch-and-Bound search tree at the time when the algorithm has discovered the optimal tour is shown below.
Each node in the search tree displays an edge (either XY or ~XY), a cost value, and a unique reference number (a1, b1, b2, ..., c1, ..., d1, ..., e1, e2). Use the reference numbers to break ties. When required, enter the reference numbers in short answers.
What information can you glean from the search tree? Answer the sub-questions based on the information gleaned from the search tree.

Determine the number of cities in the TSP instance. Enter the number of cities in the text box, or enter NIL if it is not possible to determine the number of cities.
Enter an integer.
NO SPACES, TABS, DOTS, BRACKETS OR EXTRANEOUS CHARACTERS.
Answer format: 42

Show answer

Correct answer: 5

Question 11

+1 markWritten answer

TSP Branch-and-Bound
The TSP Branch-and-Bound algorithm is solving a TSP instance where the cities are A, B, C, .... and so on. The Branch-and-Bound search tree at the time when the algorithm has discovered the optimal tour is shown below.
Each node in the search tree displays an edge (either XY or ~XY), a cost value, and a unique reference number (a1, b1, b2, ..., c1, ..., d1, ..., e1, e2). Use the reference numbers to break ties. When required, enter the reference numbers in short answers.
What information can you glean from the search tree? Answer the sub-questions based on the information gleaned from the search tree.

Start from city A, what is the path representation of the optimal tour? Enter the path
representation in the text box, or enter NIL if it is not possible to determine the optimal tour. Enter a comma separated list of cities (city labels).
NO SPACES, TABS, DOTS, BRACKETS OR EXTRANEOUS CHARACTERS.
Answer format: A,B,C

Show answer

Correct answer: A,B,D,E,C or A,C,E,D,B

Question 12

+1 markOne or more correct options

GAMES
The figure shows a game tree with evaluation function values at the leaf nodes.
The leaf nodes are labeled from A to K.
Use these labels to enter a leaf node or a list of leaf nodes in short answers (textbox). Tie-breaker:
When several nodes carry the same best cost then select the deepest node, if tie persists then select the leftmost of the deepest nodes to break the tie.

Based on the above data, answer the given subquestions.

Which of the following is a strategy for the MAX player?

Select all that apply.

  1. A

    D,E,F,G

  2. B

    H,I,J,K

  3. C

    D,E,F

  4. D

    H,I

Show answer

Correct answers

  • C

    D,E,F

  • D

    H,I

Question 13

+1 markWritten answer

GAMES
The figure shows a game tree with evaluation function values at the leaf nodes.
The leaf nodes are labeled from A to K.
Use these labels to enter a leaf node or a list of leaf nodes in short answers (textbox). Tie-breaker:
When several nodes carry the same best cost then select the deepest node, if tie persists then select the leftmost of the deepest nodes to break the tie.

Based on the above data, answer the given subquestions.

List the leaf nodes in the best strategy for MAX. Enter the node labels in alphabetical order. Enter a comma separated list of node labels in alphabetical order.
NO SPACES, TABS, DOTS, BRACKETS OR EXTRANEOUS CHARACTERS.
Answer format: X,Y,Z

Show answer

Correct answer: A,C

Question 14

+1 markWritten answer

GAMES
The figure shows a game tree with evaluation function values at the leaf nodes.
The leaf nodes are labeled from A to K.
Use these labels to enter a leaf node or a list of leaf nodes in short answers (textbox). Tie-breaker:
When several nodes carry the same best cost then select the deepest node, if tie persists then select the leftmost of the deepest nodes to break the tie.

Based on the above data, answer the given subquestions.

List the leaf nodes inspected by Alpha-Beta algorithm.
Enter a comma separated list of node labels in alphabetical order.
NO SPACES, TABS, DOTS, BRACKETS OR EXTRANEOUS CHARACTERS.
Answer format: X,Y,Z

Show answer

Correct answer: A,B,D,H

Question 15

+1 markWritten answer

GAMES
The figure shows a game tree with evaluation function values at the leaf nodes.
The leaf nodes are labeled from A to K.
Use these labels to enter a leaf node or a list of leaf nodes in short answers (textbox). Tie-breaker:
When several nodes carry the same best cost then select the deepest node, if tie persists then select the leftmost of the deepest nodes to break the tie.

Based on the above data, answer the given subquestions.

List the leaf nodes SOLVED by SSS*.
Enter a comma separated list of node labels in alphabetical order.
NO SPACES, TABS, DOTS, BRACKETS OR EXTRANEOUS CHARACTERS.
Answer format: X,Y,Z

Show answer

Correct answer: A,B,D,H or A,D,H,B or D,H,A,B

Question 16

+1 markWritten answer

PROBLEM DECOMPOSITION
The figure shows an AND-OR graph that depicts how a problem S can be decomposed into one or more smaller problems. Nodes are uniquely identified by labels (S, A, B, …). The number in each node is the heuristic estimate of the cost of solving that node.
Nodes shown in double lines are primitive nodes and their values are actual costs. Observe that a primitive node is added to the graph by its parent when the parent is expanded, and the primitive node is labeled as SOLVED and it will not be expanded subsequently.
The cost of each edge is 10 units.
Tie-breaker 1: If several nodes have the same cost then break the tie using node labels. Tie-breaker 2: For AND nodes, expand the unsolved branch with the highest cost

Enter a comma separated list of node labels.
NO SPACES, TABS, DOTS, BRACKETS OR EXTRANEOUS CHARACTERS.
Answer format: X,Y,Z

Show answer

Correct answer: S,C,B or C,B

Question 17

+1 markWritten answer

PROBLEM DECOMPOSITION
The figure shows an AND-OR graph that depicts how a problem S can be decomposed into one or more smaller problems. Nodes are uniquely identified by labels (S, A, B, …). The number in each node is the heuristic estimate of the cost of solving that node.
Nodes shown in double lines are primitive nodes and their values are actual costs. Observe that a primitive node is added to the graph by its parent when the parent is expanded, and the primitive node is labeled as SOLVED and it will not be expanded subsequently.
The cost of each edge is 10 units.
Tie-breaker 1: If several nodes have the same cost then break the tie using node labels. Tie-breaker 2: For AND nodes, expand the unsolved branch with the highest cost

Determine the value of the start node S after each node is expanded. Enter the value of S after each node is expanded.
Enter a comma separated list of numbers.
NO SPACES, TABS, DOTS, BRACKETS OR EXTRANEOUS CHARACTERS.
Answer format: 12,42,17

Show answer

Correct answer: 45,50,80 or 50,80

Question 18

+1 markNumerical answer

PROBLEM DECOMPOSITION
The figure shows an AND-OR graph that depicts how a problem S can be decomposed into one or more smaller problems. Nodes are uniquely identified by labels (S, A, B, …). The number in each node is the heuristic estimate of the cost of solving that node.
Nodes shown in double lines are primitive nodes and their values are actual costs. Observe that a primitive node is added to the graph by its parent when the parent is expanded, and the primitive node is labeled as SOLVED and it will not be expanded subsequently.
The cost of each edge is 10 units.
Tie-breaker 1: If several nodes have the same cost then break the tie using node labels. Tie-breaker 2: For AND nodes, expand the unsolved branch with the highest cost

What is the final value of the start node S computed by AO*?
Enter a number.
NO SPACES, TABS, DOTS, BRACKETS OR EXTRANEOUS CHARACTERS.
Answer format: 17

Show answer

Correct answer: 80

Question 19

+1 markOne or more correct options

RULE BASED EXPERT SYSTEMS
A Rete Net for a rule based system to identify engines, turbines and motors is shown in the figure. BoM refers to Bill-of-Materials, which is a list of parts and their quantities needed for assembling a machine.
The nodes in the network are uniquely identified by labels: A1,A2,... for Alpha nodes; B1,B2,... for beta nodes; R1,R2,... for rules.

The Working Memory contains the following WMEs uniquely identified by timestamps (sequence numbers). Assume that WMEs reside in the appropriate Alpha node, and Beta nodes simply point to elements in the ancestor Alpha nodes.

The sub-questions are based on the first Match-Resolve-Execute cycle. Determine the locations of the WMEs and compute the conflict set, then answer the sub-questions.

Which of the following rule-data tuples occur in the conflict set?

Select all that apply.

  1. A

    (Diesel-Engine, 101, 107)

  2. B

    (Petrol-Engine, 107, 102)

  3. C

    (Engine, 107)

  4. D

    (Single-Phase-Motor, 105, 104)

  5. E

    (Motor, 104)

  6. F

    (Motor, 106)

Show answer

Correct answers

  • C

    (Engine, 107)

  • D

    (Single-Phase-Motor, 105, 104)

  • E

    (Motor, 104)

  • F

    (Motor, 106)

Question 20

+1 markOne correct option

RULE BASED EXPERT SYSTEMS
A Rete Net for a rule based system to identify engines, turbines and motors is shown in the figure. BoM refers to Bill-of-Materials, which is a list of parts and their quantities needed for assembling a machine.
The nodes in the network are uniquely identified by labels: A1,A2,... for Alpha nodes; B1,B2,... for beta nodes; R1,R2,... for rules.

The Working Memory contains the following WMEs uniquely identified by timestamps (sequence numbers). Assume that WMEs reside in the appropriate Alpha node, and Beta nodes simply point to elements in the ancestor Alpha nodes.

The sub-questions are based on the first Match-Resolve-Execute cycle. Determine the locations of the WMEs and compute the conflict set, then answer the sub-questions.

If the Inference Engine uses Specificity for conflict resolution then which rule-data tuple will fire in the first round?

  1. A

    (Diesel-Engine, 101, 107)

  2. B

    (Petrol-Engine, 107, 102)

  3. C

    (Engine, 107)

  4. D

    (Single-Phase-Motor, 105, 104)

  5. E

    (Motor, 104)

  6. F

    (Motor, 106)

Show answer

Correct answer

  • D

    (Single-Phase-Motor, 105, 104)

Question 21

+1 markOne correct option

RULE BASED EXPERT SYSTEMS
A Rete Net for a rule based system to identify engines, turbines and motors is shown in the figure. BoM refers to Bill-of-Materials, which is a list of parts and their quantities needed for assembling a machine.
The nodes in the network are uniquely identified by labels: A1,A2,... for Alpha nodes; B1,B2,... for beta nodes; R1,R2,... for rules.

The Working Memory contains the following WMEs uniquely identified by timestamps (sequence numbers). Assume that WMEs reside in the appropriate Alpha node, and Beta nodes simply point to elements in the ancestor Alpha nodes.

The sub-questions are based on the first Match-Resolve-Execute cycle. Determine the locations of the WMEs and compute the conflict set, then answer the sub-questions.

If the Inference Engine uses Recency for conflict resolution which rule-data tuple will fire in the first round?

  1. A

    (Diesel-Engine, 101, 107)

  2. B

    (Petrol-Engine, 107, 102)

  3. C

    (Engine, 107)

  4. D

    (Single-Phase-Motor, 105, 104)

  5. E

    (Motor, 104)

  6. F

    (Motor, 106)

Show answer

Correct answer

  • C

    (Engine, 107)

Question 22

+1 markOne or more correct options

AUTOMATED PLANNING
The domain description of a Blocks World with a single one-armed robot is given below.

text
PREDICATES
armEmpty The arm is not holding any block, it is empty.
holding(X) The arm is holding X.
onTable(X) X is on the table.
clear(X) X has nothing above it, it is clear.
on(X,Y) X is directly placed on Y.
OPERATORS
Pickup(X): pick up X from the table.
Preconditions: { armEmpty, clear(X), onTable(X) }
Add Effects : { holding(X) }
Del Effects : { armEmpty, onTable(X) }
Putdown(X): place X on the table.
Preconditions: { holding(X) }
Add Effects : { armEmpty, onTable(X) }
Del Effects : { holding(X) }
Unstack(X,Y): pick up X that is directly sitting on Y.
Preconditions: { armEmpty, clear(X), on(X,Y) }
Add Effects : { clear(Y), holding(X) }
Del Effects : { armempty, on(X,Y) }
Stack(X,Y): place X directly on top of Y.
Preconditions: { holding(X), clear(Y) }
Add Effects : { armEmpty, on(X,Y) }
Del Effects : { holding(X), clear(Y) }

Based on the above data, answer the given subquestions.

Which of the following are applicable actions in the start state?

Select all that apply.

  1. A

    Putdown(D)

  2. B

    Unstack(D, B)

  3. C

    Unstack(C, A)

  4. D

    Pickup(E)

  5. E

    Pickup(A)

  6. F

    Stack(B, A)

  7. G

    Stack(A, C)

Show answer

Correct answers

  • B

    Unstack(D, B)

  • C

    Unstack(C, A)

  • D

    Pickup(E)

Question 23

+1 markOne or more correct options

AUTOMATED PLANNING
The domain description of a Blocks World with a single one-armed robot is given below.

text
PREDICATES
armEmpty The arm is not holding any block, it is empty.
holding(X) The arm is holding X.
onTable(X) X is on the table.
clear(X) X has nothing above it, it is clear.
on(X,Y) X is directly placed on Y.
OPERATORS
Pickup(X): pick up X from the table.
Preconditions: { armEmpty, clear(X), onTable(X) }
Add Effects : { holding(X) }
Del Effects : { armEmpty, onTable(X) }
Putdown(X): place X on the table.
Preconditions: { holding(X) }
Add Effects : { armEmpty, onTable(X) }
Del Effects : { holding(X) }
Unstack(X,Y): pick up X that is directly sitting on Y.
Preconditions: { armEmpty, clear(X), on(X,Y) }
Add Effects : { clear(Y), holding(X) }
Del Effects : { armempty, on(X,Y) }
Stack(X,Y): place X directly on top of Y.
Preconditions: { holding(X), clear(Y) }
Add Effects : { armEmpty, on(X,Y) }
Del Effects : { holding(X), clear(Y) }

Based on the above data, answer the given subquestions.

Which of the following are relevant actions in the goal state?

Select all that apply.

  1. A

    Putdown(D)

  2. B

    Unstack(D, B)

  3. C

    Unstack(C, A)

  4. D

    Pickup(E)

  5. E

    Pickup(A)

  6. F

    Stack(B, A)

  7. G

    Stack(A , C)

Show answer

Correct answers

  • F

    Stack(B, A)

  • G

    Stack(A , C)

Question 24

+1 markOne or more correct options

AUTOMATED PLANNING
The domain description of a Blocks World with a single one-armed robot is given below.

text
PREDICATES
armEmpty The arm is not holding any block, it is empty.
holding(X) The arm is holding X.
onTable(X) X is on the table.
clear(X) X has nothing above it, it is clear.
on(X,Y) X is directly placed on Y.
OPERATORS
Pickup(X): pick up X from the table.
Preconditions: { armEmpty, clear(X), onTable(X) }
Add Effects : { holding(X) }
Del Effects : { armEmpty, onTable(X) }
Putdown(X): place X on the table.
Preconditions: { holding(X) }
Add Effects : { armEmpty, onTable(X) }
Del Effects : { holding(X) }
Unstack(X,Y): pick up X that is directly sitting on Y.
Preconditions: { armEmpty, clear(X), on(X,Y) }
Add Effects : { clear(Y), holding(X) }
Del Effects : { armempty, on(X,Y) }
Stack(X,Y): place X directly on top of Y.
Preconditions: { holding(X), clear(Y) }
Add Effects : { armEmpty, on(X,Y) }
Del Effects : { holding(X), clear(Y) }

Based on the above data, answer the given subquestions.

In the planning graph, which of the following are mutex action pairs in Layer 1?

Select all that apply.

  1. A

    Unstack(D, B), Pickup(E)

  2. B

    Unstack(D, B), Unstack(C, A)

  3. C

    Pickup(E), Stack(B, A)

  4. D

    Pickup(E), Stack(A, C)

Show answer

Correct answers

  • A

    Unstack(D, B), Pickup(E)

  • B

    Unstack(D, B), Unstack(C, A)

Question 25

+1 markOne or more correct options

AUTOMATED PLANNING
The domain description of a Blocks World with a single one-armed robot is given below.

text
PREDICATES
armEmpty The arm is not holding any block, it is empty.
holding(X) The arm is holding X.
onTable(X) X is on the table.
clear(X) X has nothing above it, it is clear.
on(X,Y) X is directly placed on Y.
OPERATORS
Pickup(X): pick up X from the table.
Preconditions: { armEmpty, clear(X), onTable(X) }
Add Effects : { holding(X) }
Del Effects : { armEmpty, onTable(X) }
Putdown(X): place X on the table.
Preconditions: { holding(X) }
Add Effects : { armEmpty, onTable(X) }
Del Effects : { holding(X) }
Unstack(X,Y): pick up X that is directly sitting on Y.
Preconditions: { armEmpty, clear(X), on(X,Y) }
Add Effects : { clear(Y), holding(X) }
Del Effects : { armempty, on(X,Y) }
Stack(X,Y): place X directly on top of Y.
Preconditions: { holding(X), clear(Y) }
Add Effects : { armEmpty, on(X,Y) }
Del Effects : { holding(X), clear(Y) }

Based on the above data, answer the given subquestions.

In the planning graph, which of the following are mutex proposition pairs in Layer 1?

Select all that apply.

  1. A

    clear(B), holding(C)

  2. B

    clear(B), clear(A)

  3. C

    clear(E), on(D, B)

  4. D

    clear(E), holding(D)

Show answer

Correct answers

  • A

    clear(B), holding(C)

  • B

    clear(B), clear(A)

Question 26

+1 markOne correct option

CONSTRAINT SATISFACTION

Consider a map colouring problem with 3 regions {A,B,C}, where all three regions are adjacent to each other, and the regions are being processed in the order A,B,C.

The domains are:

DA={r,b,g}D_A = \{r, b, g\}

DB={r,b}D_B = \{r, b\}

DC={r,b}D_C = \{r, b\}

Draw the constraint graph for the above problem and answer the sub-questions.

Is the given CSP arc consistent?

  1. A

    Yes

  2. B

    No

  3. C

    Cannot be determined

Show answer

Correct answer

  • A

    Yes

Question 27

+1 markOne correct option

CONSTRAINT SATISFACTION

Consider a map colouring problem with 3 regions {A,B,C}, where all three regions are adjacent to each other, and the regions are being processed in the order A,B,C.

The domains are:

DA={r,b,g}D_A = \{r, b, g\}

DB={r,b}D_B = \{r, b\}

DC={r,b}D_C = \{r, b\}

Draw the constraint graph for the above problem and answer the sub-questions.

Is the given CSP path consistent?

  1. A

    No

  2. B

    Yes

  3. C

    Cannot be determined

Show answer

Correct answer

  • A

    No

Question 28

+1 markWritten answer

CONSTRAINT SATISFACTION

Consider a map colouring problem with 3 regions {A,B,C}, where all three regions are adjacent to each other, and the regions are being processed in the order A,B,C.

The domains are:

DA={r,b,g}D_A = \{r, b, g\}

DB={r,b}D_B = \{r, b\}

DC={r,b}D_C = \{r, b\}

Draw the constraint graph for the above problem and answer the sub-questions.

Does the given CSP have a solution? Enter the solution for regions A,B,C as a comma separated list of colours. Enter NIL if there is no solution.
NO SPACES, TABS, DOTS, BRACKETS OR EXTRANEOUS CHARACTERS.
Answer format: r,b,r

Show answer

Correct answer: g,r,b or g,b,r