Labyrinth
Rules[edit]
Place numbers from 1-N in all the cells in the grid so that the numbers do not repeat in any row and column. Then draw a closed loop that travels horizontally and vertically between the centres of adjacent cells and visits every cell exactly once. The numbers along the loop must follow the worm rule of alternating higher and lower values. The numbers on the left show the sums of the numbers on the loop segments in the given row (in the correct order).
(Rules and example (N=4) from WPC 2018 IB)
Rule variations[edit]
- With Obstacles: Some cells may remain empty. The number of "obstacles" is given.
History of the puzzle[edit]
Appeared on WPC 2018/Round 12, an "innovatives" round. The puzzle was written by František Luskač (Czech Rep.).
This type of combination between the loop genre and Japanese Sums was already present in 2016, first appearing in the 2016 MIT Mystery Hunt.[1] The puzzle was co-written by Eric Prestemon (USA) and Craig Kasper (Canada).
However, the Mystery Hunt version doesn't require all cells to be used by the path and doesn't have the "worm" rule of alternation, which probably was inspired by Worms, another invention of František Luskač.
Confusingly, another number placement puzzle with the name Rollercoaster appeared on WPC 2015/Round 3.
Appearances in the past WPCs[edit]
- WPC 2018/Round 12 (both with and without obstacles) by František Luskač