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Bottom-Up and LR Parsing PYQs for GATE CS

Solve 8+ Bottom-Up and LR Parsing previous year questions for GATE CS with answers and detailed solutions. Free sample questions below.

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Question 1

2026 Slot Set2 PYQ

Consider the canonical L R (0) parsing of the grammar below using terminals {a, b, c} and non-terminals {A, B, C, S} with S as the start symbol. S \to A C B A \to a A ∣ ϵ C \to c C ∣ ϵ B \to b B ∣ b Which one of the following options gives the number of shift-reduce conflicts that will occur in the L R (0) ACTION table?

Question 2

2025 Slot Set2 PYQ

Given a Context-Free Grammar G as follows: S \to A a ∣ b A c ∣ d c ∣ b d a A \to d Which ONE of the following statements is TRUE?

Question 3

2024 Slot Set2 PYQ

Consider the following augmented grammar, which is to be parsed with a SLR parser. The set of terminals is {a, b, c, d, #, @} S^{'} S A B \to S \to S S ∣ A a ∣ b A c ∣ B c ∣ b B a \to d # \to @ Let I_{0} = C L O S U R E ({S^{'} \to ∙ S}) . The number of items in the set GO T O (I_{0}, S) is __________

Question 4

2024 Slot Set1 PYQ

Which of the following is/are Bottom-Up Parser(s)?

Question 5

2024 Slot Set1 PYQ

Consider the operator precedence and associativity rules for the integer arithmetic operators given in the table below. Operator Precedence Associativity + Highest Left - High Right * Medium Right / Low Right The value of the expression 3 + 1 + 5 * 2/7 + 2 - 4 - 7 - 6/2 as per the above rules is __________

Question 6

2022 PYQ

Consider the augmented grammar with {+, *, (,), i d} as the set of terminals. S^{'} S R P \to S \to S + R ∣ R \to R * P ∣ P \to (S) ∣ i d If I_{0} is the set of two L R (0) items {[S^{'} \to S \cdot], [S \to S \cdot + R]}, then g o t o (c l os u r e (I_{0}), +) contains exactly __________ items.

Question 7

2021 Slot Set2 PYQ

Consider the following augmented grammar with {#, @, <, >, a, b, c} as the set of terminals. S^{'} \to S S \to S # c S S \to S S S \to S @ S \to< S > S \to a S \to b S \to c Let I_{0} = CLOSURE ({S^{'} \to ∙ S}) . The number of items in the set GOTO (GOTO (I_{0}, <), <) is __________.

Question 8

2021 Slot Set1 PYQ

Consider the following statements. S_{1} : Every SLR(1) grammar is unambiguous but there are certain unambiguous grammars that are not SLR(1). S_{2} : For any context-free grammar, there is a parser that takes at most O (n^{3}) time to parse a string of length n . Which one of the following options is correct?

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Bottom-Up and LR Parsing PYQs for GATE CS

Solve 8+ Bottom-Up and LR Parsing previous year questions for GATE CS with answers and detailed solutions. Free sample questions below.

Chapter Roadmap: Bottom-Up and LR Parsing

Building the parse tree from leaves to root: rightmost derivation in reverse.

Your Learning Journey

1. Bottom-Up Parser Types and LR Grammar Classes

The foundation. Understanding handle pruning, rightmost derivations in reverse, and the strict hierarchy of LR(0), SLR(1), LALR(1), and CLR(1) parsers.

2. Operator Precedence and Shift-Reduce Parsing

The mechanics. How shift-reduce parsing works in practice, identifying handles, and the specialized rules of operator precedence grammars.

3. LR Item Closure and GOTO Computation

The engine. Step-by-step construction of canonical collections of LR items, the CLOSURE operation, and the GOTO function that builds the parsing DFA.

4. LR Parsing Conflicts and Grammar Ambiguity

The resolution. Identifying shift-reduce and reduce-reduce conflicts, understanding why they occur, and techniques to resolve them or prove a grammar is not LR.

Chapter Weightage: High. Expect 1 to 2 questions directly testing LR item construction, conflict identification, or grammar class hierarchy.

Bottom-Up Parser Types and LR Grammar Classes

Why this matters: Bottom-up parsing is the most powerful class of deterministic parsing. It forms the basis of almost all automatic parser generators (like YACC and Bison) used in real-world compilers.

What you will learn here

The core concept of "handle pruning" and rightmost derivation in reverse
The meaning of the L, R, and k in LR(k) parsing
The strict hierarchy of LR grammar classes: LR(0), SLR(1), LALR(1), and CLR(1)
How lookahead power trades off with the number of parser states

Chapter context: Parser Types and LR Classes → Shift-Reduce Mechanics → Item Closure and GOTO → Conflict Resolution

Bottom-Up and LR Parsing: Solved Questions with Step-by-Step Explanations (8 Problems)

Question 1 · Compiler Design · 2026_Set2 MCQ

Consider the canonical

L R (0)

parsing of the grammar below using terminals

{a, b, c}

and non-terminals

{A, B, C, S}

with

S

as the start symbol.

S \to A C B

A \to a A ∣ ϵ

C \to c C ∣ ϵ

B \to b B ∣ b

Which one of the following options gives the number of shift-reduce conflicts that will occur in the

L R (0)

ACTION table?

A.
2
B.
3
C.
4
D.
5

Question 2 · Compiler Design · 2025_Set2 MCQ

Given a Context-Free Grammar

G

as follows:

S \to A a ∣ b A c ∣ d c ∣ b d a

A \to d

Which ONE of the following statements is TRUE?

A.
$G$ is neither LALR(1) nor SLR(1)
B.
$G$ is CLR(1), not LALR(1)
C.
$G$ is LALR(1), not SLR(1)
D.
$G$ is LALR(1), also SLR(1)

Question 3 · Compiler Design · 2024_Set2 NAT

Consider the following augmented grammar, which is to be parsed with a SLR parser. The set of terminals is ${a, b, c, d, #, @}$

$S^{'} S A B \to S \to S S ∣ A a ∣ b A c ∣ B c ∣ b B a \to d # \to @$

Let $I_{0} = C L O S U R E ({S^{'} \to ∙ S})$ . The number of items in the set $GO T O (I_{0}, S)$ is __________

Question 4 · Compiler Design · 2024_Set1 MSQ

Which of the following is/are Bottom-Up Parser(s)?

A.
Shift-reduce Parser
B.
Predictive Parser
C.
LL(1) Parser
D.
LR Parser

Question 5 · Compiler Design · 2024_Set1 NAT

Consider the operator precedence and associativity rules for the integer arithmetic operators given in the table below.

The value of the expression

3 + 1 + 5 * 2/7 + 2 - 4 - 7 - 6/2

as per the above rules is __________

Question 6 · Compiler Design · 2022 NAT

Consider the augmented grammar with ${+, *, (,), i d}$ as the set of terminals.

$S^{'} S R P \to S \to S + R ∣ R \to R * P ∣ P \to (S) ∣ i d$

If $I_{0}$ is the set of two $L R (0)$ items ${[S^{'} \to S \cdot], [S \to S \cdot + R]}$ , then $g o t o (c l os u r e (I_{0}), +)$ contains exactly __________ items.

Question 7 · Compiler Design · 2021_Set2 NAT

Consider the following augmented grammar with

{#, @, <, >, a, b, c}

as the set of terminals.

S^{'} \to S

S \to S # c S

S \to S S

S \to S @

S \to< S >

S \to a

S \to b

S \to c

Let

I_{0} = CLOSURE ({S^{'} \to ∙ S})

. The number of items in the set

GOTO (GOTO (I_{0}, <), <)

is __________.

Question 8 · Compiler Design · 2021_Set1 MCQ

Consider the following statements.

S_{1} :

Every SLR(1) grammar is unambiguous but there are certain unambiguous grammars that are not SLR(1).

S_{2} :

For any context-free grammar, there is a parser that takes at most

O (n^{3})

time to parse a string of length

n

.

Which one of the following options is correct?

A.
$S_{1}$ is true and $S_{2}$ is false
B.
$S_{1}$ is false and $S_{2}$ is true
C.
$S_{1}$ is true and $S_{2}$ is true
D.
$S_{1}$ is false and $S_{2}$ is false

Try a question

Login to view the complete previous-year questions and solutions

Personalised first. High quality throughout.

Built around you, not around a syllabus PDF

Revision that hits your weak spots

Questions calibrated to the real exam

Notes written for recall, not for volume

One place for everything

Honest progress

Unlock the whole course

Bottom-Up and LR Parsing PYQs for GATE CS

Chapter Roadmap: Bottom-Up and LR Parsing

Chapter Roadmap: Bottom-Up and LR Parsing

Your Learning Journey

Bottom-Up Parser Types and LR Grammar Classes

Bottom-Up Parser Types and LR Grammar Classes

What you will learn here

Bottom-Up and LR Parsing: Solved Questions with Step-by-Step Explanations (8 Problems)

More previous year questions (pyqs) in this unit