VLSI DV Interview Puzzles · All levels

Queue Mutation Plus Dynamic Resize

Compute final `q`, `deleted`, and `da` after all operations.

Puzzle

Difficulty: Easy · Puzzle 1 of 6 · Topic: Queue and Array Puzzles

Compute final `q`, `deleted`, and `da` after all operations.

Code

systemverilog

module p1;
  int q[$] = '{1,2,3};
  int da[] = '{10,20,30,40};
  int deleted;
  initial begin
    q.push_front(9);        // {9,1,2,3}
    q.insert(2, 77);        // {9,1,77,2,3}
    deleted = q.pop_back(); // deleted=3, q={9,1,77,2}
    q.delete(1);            // {9,77,2}

    da = new[2](da);        // {10,20}
    da = new[5](da);        // {10,20,0,0,0}
    $display("q=%p deleted=%0d da=%p", q, deleted, da);
  end
endmodule

Hint

Queue methods mutate immediately; dynamic-array `new[N](old)` copies only prefix `min(old.size, N)`.

Step-by-step solution

diagram

1) Queue operations produce `{9,77,2}` and popped value 3.
2) Resizing to 2 truncates dynamic array to first two elements.
3) Resizing to 5 extends that truncated array and default-initializes new slots to 0.

Answer

Answer: q=' {9,77,2}, deleted=3, da=' {10,20,0,0,0}

Why candidates get it wrong

People expect second resize to recover old truncated elements, but they are already lost.

Interviewer follow-up

How can you preserve full original data before truncating a dynamic array?

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