Hardware interview practice
Count target-sum bursts
Count every nonempty contiguous range in a frame of signed occupancy changes whose sum equals a programmable target. Overlapping ranges and multiple matches ending at one sample all count.
Reviewed example
Work through one case
Input
signed deltas = [1, -1, 1, -1]; target=0Expected output
matching contiguous ranges=4Prefix values are [0,1,0,1,0]; equal-prefix pairs contribute three zero-prefix pairs and one one-prefix pair.
What to cover
Requirements
- Support 1 to 32 signed eight-bit deltas, a signed 13-bit target, and a 10-bit result up to 528.
- Insert the initial zero prefix before processing the first sample.
- Count every previous occurrence of current_prefix - target, including repeated equal prefixes.
- Sign-extend to 14 bits for the subtraction and comparison so the lookup key cannot wrap.
- Use fixed bounded storage and hold the final count stable under backpressure.