Hidoku

Hidoku Instructions:
Here's how to play Hidoku:
Place a number into every empty square in the grid, in such a way that a continuous path from cell 1 to cell n can be traced in accordance with the allowed moves.

With standard hidoku puzzles, each move must only be from one cell to an adjacent cell, including diagonally touching cells, eg for a cell in the centre of the grid there will eight options available.

Each cell must be visited exactly once and it must be possible to travel from the first cell to the last cell continuously once the puzzle is solved.

Hidoku, the Travelling Puzzle

Travelling puzzles have a long history, and hidoku in various different forms goes back a long way.

The first mention of this puzzle in the puzzle literature seems to go back to chess puzzles from literally many centuries ago, and whilst the knight's journey around the grid is perhaps more famous, the king's journey was also a well-known puzzle type.

And indeed the standard hidoku rules are simply that of working out a king's journey as it moves around the board, visiting each square exactly once (the king moves in the same way: one square at a time in any direction). Indeed on our main puzzles page you'll see this puzzle listed as king's journey.

With hidoku puzzles, it is often the case that the first and last cells of the journey are listed, although this is not necessarily the case. Certainly some moves along the route are given, this is necessary to ensure that there is only one solution that can be reached through the application of logical rules alone.

Solving hidoku requires one to look at the possible routes between sets of given cells, and see if there are any clues available as to the route that must be taken.

This could be very straightforward - such as seeing that there is only one route available - or it may be more complex and require one to consider if one section of the grid would get cut-off from another if a certain path were taken, and therefore another path must be taken.

Looking at the corners and working out ways in and out of the corners can often bear fruit. Also look for numbers where there is only one possible route in and out rather than several to get some easy quick placements at the start.

One would not expect to work from the start right to the end but rather gradually build up bits of the path in stages and then only connect them together as the options start to reduce towards the end.

Related puzzles

Fillomino, Hashi, Kakuro, Nonogram

Last updated: 17 Feb 2012

Back to A - Z of puzzles

Sample puzzle:
start Hidoku image

Sample solution:
solution Hidoku image

View a sample Hidoku PDF

Play Hidoku Puzzles:

To play hidoku puzzles online, then take a look at the Hidoku Puzzles at the Puzzle Club - that link goes through to a 20 x 20 puzzle, there are lots of smaller ones available to play online.

For print puzzles, then download and print off our Hidoku Magazine which contains a combination of 8 x 8 hidoku puzzles and knights tour puzzles.

Publish Hidoku Puzzles:

If you would like to buy or licence Hidoku puzzles for publication, then please Contact Us >>>