From WPC unofficial wiki


Draw a single closed loop into the grid that only travels horizontally or vertically, passes all squares, and does not cross or overlap itself. The loop must contain the given fragments.

(Rules and example from WPC 2005 IB)

History of the puzzle[edit]

In terms of graph theory, this is a variant of the Hamiltonian path problem on grid graphs. This concept is named for William Rowan Hamilton (Ireland) for inventing the icosian game in 1857.

While this puzzle can be seen as a variation of Simple Loop, this puzzle was also published by Steve "Stitch" Wilson in around 1990 under the name "Grand Tour".[1] It is possible that the puzzle has been independently invented multiple times, due to the simplicity of the rules.

Appearances in the past WPCs[edit]