GATE CS 2026 Set 1 — Question 28

MSQ+1 / -0MediumLL(1) ParsingSyntax AnalysisCompiler Design

Compiler Design → Syntax Analysis → LL(1) Parsing

Last updated 5 September 2026

Question

Which of the following statements is/are true?

Correct answer (C) For a grammar to be LL(1), it must be left-factored Solution Statement (A) is false because LL(1) parsers are predictive parsers that use a lookahead of 1 symbol to determine the production to apply, without backtracking. Statement (B) is false because left-recursion causes an infinite loop in LL(1) parsers. A grammar must be free of left-recursion to be LL(1). Statement (C) is true. A grammar must be left-factored (i.e., have no common prefixes in the right-hand sides of productions for the same non-terminal) to be LL(1), otherwise the parser cannot deterministically choose a production based on a single lookahead. Statement (D) is false. SLR parsers (which are bottom-up) are generally more powerful than LL(1) parsers (which are top-down). Turn this into a strength. Explore AI-powered practice and doubt support with Success Tracker.

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Correct answer (C) For a grammar to be LL(1), it must be left-factored Solution Statement (A) is false because LL(1) parsers are predictive parsers that use a lookahead of 1 symbol to determine the production to apply, without backtracking. Statement (B) is false because left-recursion causes an infinite loop in LL(1) parsers. A grammar must be free of left-recursion to be LL(1). Statement (C) is true. A grammar must be left-factored (i.e., have no common prefixes in the right-hand sides of productions for the same non-terminal) to be LL(1), otherwise the parser cannot deterministically choose a production based on a single lookahead. Statement (D) is false. SLR parsers (which are bottom-up) are generally more powerful than LL(1) parsers (which are top-down).

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