GATE CS 2026 Set 2 Q.35: Lexical Analysis

A lexical analyzer uses the following token definitions

$letter \rightarrow [A-Za-z]$
$digit \rightarrow [0-9]$
$id \rightarrow letter (letter \mid digit)^*$
$number \rightarrow digit^+$
$ws \rightarrow (blank \mid tab \mid newline)^+$

For the string given below,
x1 23mm 78 y 7z zz5 14A 8H AaYcD
the number of tokens (excluding $ws$ ) that will be produced by the lexical analyzer is __________. (answer in integer)

Your answer

Official answer and solution

Official answer: 13
From: Official GATE 2026 answer key

Solution

Apply the longest-match (maximal munch) rule to each whitespace-separated chunk.

By the maximal-munch rule, a chunk starting with a digit matches $number$ up to the first letter, and the remaining suffix starting with a letter matches $id$ :

x1 $\rightarrow$ <id, x1> (1 token)
23mm $\rightarrow$ <number, 23>, <id, mm> (2 tokens)
78 $\rightarrow$ <number, 78> (1 token)
y $\rightarrow$ <id, y> (1 token)
7z $\rightarrow$ <number, 7>, <id, z> (2 tokens)
zz5 $\rightarrow$ <id, zz5> (1 token)
14A $\rightarrow$ <number, 14>, <id, A> (2 tokens)
8H $\rightarrow$ <number, 8>, <id, H> (2 tokens)
AaYcD $\rightarrow$ <id, AaYcD> (1 token)

Total tokens (excluding $ws$ ) $= 1 + 2 + 1 + 1 + 2 + 1 + 2 + 2 + 1 = 13$ .

Final answer

Common trap

Counting whitespace-separated words (9) without splitting 23mm, 7z, 14A, and 8H into <number> followed by <id>.

The answer is the one in the official GATE answer key. The solution is this site's own explanation.

Source

Paper: GATE 2026 Computer Science and Information Technology - Session 2 (CS2)
Question: 35 of 65
Section: Computer Science and Information Technology

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