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📋 Last Remaining Cell – Sudoku Technique

When a unit (row/column/box) has only one possible cell left for a digit, place it immediately. Illustrated step-by-step guide.

What Is the Last Remaining Cell?

The last remaining cell technique applies when, in a unit (row, column or 3×3 box), a digit has only one possible position left. Place that digit immediately.

Step-by-Step Example

Step 1: Focus on the top row and left column; find missing digits
1) Pick a nearly complete unit and list its missing digits.
Step 2: Column constraints force the 4 to the top-left cell
2) Column restrictions mean the 4 can only go in the top-left cell.
Step 3: Row check confirms the same single position
3) A row check confirms it’s still the only valid spot.
Step 4: Place 4 in the last remaining cell
4) Place the 4; follow-up placements often appear.

Tips

  • Works in any row, column or box.
  • Explicitly listing the missing digits makes the single spot obvious.
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