Hardware interview practice

Group diagnostic tags without dynamic allocation

MediumStringsSystemVerilog

Group as many as 32 fixed-record lowercase diagnostic tags into anagram families without heap allocation, while preserving both first-group order and member input order.

Starting point

Question code

typedef struct { byte text[17]; } diag_tag_t;

function automatic bit group_tags(
  input diag_tag_t tags[32],
  input int unsigned count,
  ref byte unsigned order[32],
  ref byte unsigned group_start[33],
  ref int unsigned group_count
);

Reviewed example

Work through one case

Input

tags=["eat","tea","tan","ate"]

Expected output

groups=[["eat","tea","ate"],["tan"]]

The letter-count key groups the three anagrams, while first-group and member encounter order remain unchanged.

What to cover

Requirements

Validate every active record before writing: a terminator must occur within 17 bytes, length must be 1 through 16, and all characters must be lowercase ASCII.
Use the exact tag length plus 26 letter counts as the grouping key rather than relying on a hash alone.
Order groups by the first member seen, preserve member order, and publish group_start[0]=0 and group_start[group_count]=count.
Use only bounded workspace and leave all outputs byte-for-byte unchanged for every invalid argument or malformed tag.