Block Assembly Checkpoint

Reconstruct single-pass selection, diagnose partial mutation, and quantify the limits of greedy fee rates.

Get every question correct to pass this checkpoint. You can review feedback, revise your answers, and submit again.

1. A child has the highest rate but its parent output is initially missing. The parent is included later. What happens in this single-pass task?

Select one answer.

The child is inserted before its parent The child is retried automatically The child stays excluded The block must be empty

2. A=(fee 11,size 5), B=(fee 9,size 4). Which candidate sorts first under the exact-rate policy?

Select one answer.

A, because 11 exceeds 9 B, because 9*5=45 exceeds 11*4=44 They tie because both integer quotients are 2 Whichever appeared first in the input

3. A candidate lists inputs [u,missing]. u is available. How should rejection affect u?

Select one answer.

Spend u and refund its fee Delete u to prevent later conflicts Create the candidate's outputs anyway Leave u available for later candidates

4. A total budget is 450 bytes, including 100-byte coinbase. Sorted independent candidates are A=(200 bytes,400 fee), B=(200,300), C=(150,150). What total fee is selected? Enter one decimal integer.

5. For that selected fee total of 550, a subsidy of 25 gives what coinbase reward? Enter one decimal integer.

6. Payload budget is 300. Independent A=(200 bytes,400 fee), B=C=(150,285). What demonstrates greedy's limitation?

Select one answer.

It selects all three within budget It selects A for 400 although B+C would yield 570 It is optimal because A has the highest rate It must violate dependency order

7. Two selected candidates would spend the same initial outpoint. What prevents accepting both?

Select one answer.

Testing both only against the initial map Their transaction IDs being distinct Deleting the first spend from the temporary available-output map Counting the input twice in TotalSize

8. Rates and fees tie. Which rule determines order while preserving the caller's mempool?

Select one answer.

Sort a copy by lexicographic ID bytes ascending Use randomized map iteration Sort the caller's slice by pointer address Choose the larger ID first

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