When a square’s row and column, and its signs, leave it only one number it could be, that’s its number. It’s the most used technique in Futoshiki, and on most grids it does more of the work than any other.
This is the first of the Futoshiki techniques. Each page shows its technique on the same 7×7 from the game, Hard level 5.
The rule
- Pick an empty square.
- Cross out every number already in its row and its column.
- Cross out whatever its signs rule out, and anything you’ve crossed out in its notes.
- If one number is left, write it in.
In a real puzzle
On the 7×7 every technique page follows, it’s first needed at step 8, straight after a what-if. The square in row 4, column 1 could only be 2 or 3, and the what-if has just ruled out 3. One number left: 2.
Most of the time it’s plainer than that: a row and a column that between them hold every number but one. Later in this puzzle, that’s how most of the grid fills in.
How often you’ll need it
On every one of the game’s 150 levels. It’s 30 of the 57 moves on the 7×7 here, and on average 12.3 moves on an Easy level, 17.4 on Medium and 29.8 on Hard.