SignalChapter 7: Frames and loops

48ROUND TRIP

The task

X is a stream of frames: each frame is a few values and then a 0.

P must receive the sum of each frame and Q how many values it held.

A lone 0 is an empty frame, with a sum and a length of 0.

The board

The board as the puzzle screen lays it out. Cyan pins read, lemon pins write, violet pins go both ways. On a narrow screen, scroll the board sideways to see all of it.

Key idea

A frame needs a sum and a count, one more value than B holds, so a counter core sits on a loop.

Hints

Each hint goes a step further than the one before. Open them one at a time.

Hint 1Show

Keep the sum in B. There is no room for the count as well.

Hint 2Show

Send every value round to k, the 0 too, so k can see where a frame ends.

Hint 3Show

k counts in its own B and sends the count back when the 0 comes.

Solution

Reveal the Full SolutionThe complete program for ROUND TRIP. Open it only when you want the answer.

The reference program

The game's own solution. It passes every test and scores exactly par on every benchmark.

hSC-2 standard

S: IN P0
OUT P3
JZ E
ADD B
MOV B, A
JMP S
E: XCH A, B
OUT P1
IN P4
OUT P2

kSC-2 standard

S: IN P0
JZ E
XCH A, B
ADD 1
MOV B, A
JMP S
E: XCH A, B
OUT P1

CYCLES: 303; at par
ENERGY: 2536; at par
NODES: 2; at par
INSTRUCTIONS: 18; at par