Snake

Rules

Draw a snake, i.e. a 1 cell-wide single continuous path in the grid whose head and tail are given. The snake does not touch itself, even diagonally. Numbers outside the grid indicate the number of snake cells in that row/column.

(Rules and example from WPC 2017 IB)

Rule Variations

There are a lot.

• Endpoints are not given.
• Length of a snake is given.
• Snake's midpoint (for example 23rd cell in a 45-cells long snake) is given.
• Some cells with snake segments are given.
• A puzzle from WPC 2018/Round 7 had "E/O" clues outside the grid that stand for even and odd.
• A puzzle from WPC 2016/Round 12 required the snake to go through every given letter in a given order.
• Snaky Loop: Instead of a snake, locate a loop that doesn't touch itself.

History of the puzzle

Probably first appeared under the name "Nessie" in WPC 1996. The author is unknown.

Variants

See list of Snake variants.

Appearances in the past WPCs

Listed here are appearances of classic to almost-classic Snakes. For variants, see list of Snake variants#Appearances in the past WPCs.

• WPC 2019/Round 2 (Toroidal Snake) by Jürgen Blume-Nienhaus
• WPC 2019/World Cup Round 1 by Roland Voigt
• WPC 2019/Round 9 by Ulrich Voigt
• WPC 2018/Round 7 by Jiří Hrdina
• WPC 2018/Round 13 (Knapp Daneben Snake) by Jiří Hrdina
• WPC 2018/Team Round 1 (Snaky Loop, part of a hybrid) by Jiří Hrdina
• WPC 2018/Team Round 3 (part of a combination puzzle) by Jiři Hrdina
• WPC 2017/Round 11 (Snake, Toroidal Snake) by Ashish Kumar
• WPC 2016/Round 2 by Matej Uher
• WPC 2016/Round 12 by Matúš Demiger
• WPC 2015/Round 2 by Hns Eendebak
• WPC 2015/Round 9 ("Different Areas") by Vladimir Portugalov