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Hardware interview practice

Intersect redundant-core fault lists

EasyFirmware AlgorithmsSystemVerilog

Return the multiset intersection of two bounded fault-ID lists, preserving the first list's encounter order and consuming each match only once.

Starting point

Question code

typedef enum { IX_OK, IX_EINVAL, IX_ENOSPC } ix_rc_t;
ix_rc_t fault_intersection(const uint16_t *a, size_t na,
                           const uint16_t *b, size_t nb,
                           uint16_t *out, size_t cap,
                           size_t *nout);
// na and nb are at most 32.
Reviewed example

Work through one case

Input
A=[5,2,5,7]; B=[5,5,8]
Expected output
intersection=[5,5]

Both copies of 5 are consumed once in A encounter order; 2 and 7 have no available match.

What to cover

Requirements

  1. Emit each identifier min(count_a, count_b) times in A's encounter order.
  2. Use fixed state for at most 32 entries and do not modify either input.
  3. Count the complete result before writing and return no-space without exposing a partial output.
  4. Validate pointers, lengths, arithmetic, and output/input overlap while preserving all outputs on error.
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