f00f

Your mission

Report where the locking pair of bytes starts in a stream of instruction bytes.

today's brief

November 1997. Somebody works out that four bytes, F0 0F C7 C8, hang any Pentium stone dead: the chip locks and only the reset line brings it back. Any user could run it. No privileges needed. Find the sequence in the instruction stream.

See it in action

lock_at({144,240,15,199,200}, 5)

Expected result

Your checklist

For your own tracking. Tests grade your code.

code holds n instruction bytes as numbers from 0 to 255.
The lock-up starts at a byte 240 that is immediately followed by a byte 15.
Return the index of the first such 240.
Return -1 when the stream does not contain the pair.

More examples

lock_at({240,15}, 2)

Expected result

lock_at({15,240}, 2)

Expected result

-1

Constraints

Expected files

stream.c

Allowed functions

None. Write every helper yourself.

Back to compete

Solutions

f00f

Your mission

Report where the locking pair of bytes starts in a stream of instruction bytes.

today's brief

See it in action

lock_at({144,240,15,199,200}, 5)

Expected result

Your checklist

For your own tracking. Tests grade your code.

code holds n instruction bytes as numbers from 0 to 255.
The lock-up starts at a byte 240 that is immediately followed by a byte 15.
Return the index of the first such 240.
Return -1 when the stream does not contain the pair.

More examples

lock_at({240,15}, 2)

Expected result

lock_at({15,240}, 2)

Expected result

-1

Constraints

Expected files

stream.c

Allowed functions

None. Write every helper yourself.

Back to compete

Solutions