Rollercoaster

Not to be confused with "Roller Coaster", a puzzle that appeared in MIT Puzzle Hunt and GM Puzzles blog. See Labyrinth.

Rules

Place the digits from 1 to N exactly once each into every row and column. Every digit should be either greater or smaller than all its adjacent neighbours.

(Rules (modified) and example (N=8) from WPC 2015 IB)

Rule variations

• In WPC 2015 puzzles, N had a fixed value of 8. Theoretically, N can take any value, though it probably cannot be an odd number. (Not a proven fact)

History of the puzzle

Its first appearance is currently unknown but earlier than 2009 Belarus Nationals, where it appeared under the name "Супер 8" (translated as Super 8).

Appearances in the past WPCs

• WPC 2015/Round 3 by Vladimir Portugalov