How to solve mini sudoku
A 6×6 sudoku solves with two scans: cells with one digit left, and digits with one place left. Alternate them until the grid is full.
How it works
A mini sudoku is a 6×6 grid. Each row, column and box holds 1 to 6 exactly once. The boxes are two rows tall and three columns wide.
Two scans solve most of them. The cell scan: find a cell whose row, column and box already show five different digits, and write the sixth. That is a naked single. The digit scan: pick a digit and a row, column or box that lacks it, and find the one place it fits. That is a hidden single.
Every digit you place feeds both scans. When neither finds anything, move to pairs and pointing.
The order that works
Start with the cell scan on the busiest rows and boxes. Then do the digit scan, one digit at a time, starting with the digit that appears most.
After every placement, look at the new digit’s row, column and box first. That is where the next single usually is.
When you get stuck
Pencil in the candidates of every empty cell. Look for two cells in a row, column or box with the same two candidates, and for a box whose places for a digit line up. If even that fails, test one cell honestly: suppose, follow forced moves, and keep only a contradiction.
Worth memorizing
Two scans: cell first, then digit.
Naked singles, then hidden singles.
Look near the last digit you placed.
Its row, column and box just changed.
Pencil marks come out when singles stall.
Then look for pairs and pointing.
Practice
0 of 4 rightAt the start, which of these cells is a naked single?
Where does 5 go in row 4?
Row 1 is done. What goes in the ringed cell?
The top half is done. What goes in the ringed cell?