KNS Puzzles offers the Neighbours puzzles in the following formats:
4 x 4 - Level 1
5 x 5 - Level 1 - Level 2
6 x 6 - Level 1 - Level 2
7 x 7 - Level 1 - Level 2
9 x 9 - Level 1
Complete the grid such that every row and column contains every number exactly once. The symbols on the grid indicate neighbours (e.g. 1 >< 2, 3 >< 4, 2 >< 1). Rule 1 - a symbol between = the numbers are neighbours. Rule 2 - NOT a symbol between = the numbers are NOT neighbours. What are the symbols for? The symbols are double arrows that point to two numbers that are neighbours of each other, e.g. 1><2, 3><2, 3><4.
This is the start of the puzzle. This example highlights the importance of the lack of a neighbour symbol.
Because the <1> has no neighbour symbols, these squares in this row cannot be <2>.
Because neither <1> has a neighbour symbol, these squares in this column cannot be <2>.
Because the <2> has a neighbour symbol, this square must be either <1> or <3>. However, there is already a <1> in both the row and column, therefore this square is the <3>.
This row and column can now be completed.
As neither the <2> nor the <4> has a neighbour symbol, these squares cannot be <3>.
This square cannot be <4>, and the row can be completed.
There is already a <4> in this row, so the <4> for this column can't go in this square, and the column completes.
Because the <1> has no neighbour symbol, this square cannot be <2>. The puzzle quickly completes.
The completed puzzle.
This square has to be <3> because of the neighbour symbol next to the <4>.
This square CANNOT be <3> because there isn't a neighbour symbol next to the <4>.
Because of the given <2> and the neighbour symbol, A can only be <1> or <3>. Therefore B could be <2> or <4> - however, B can't be 4 as the <5> has no neighbour symbol. So B must be <2> (and A is either <1> or <3>).