One Choice Method - Basic Solving Sudoku Technique
One-Choice, or Sole Candidate, or Only Candidate, or Naked Single
One-Choice by
Mensa Guide to Solving Sudoku
a.k.a. Sole
Candidate by Kristanix.com
a.k.a. Only
Candidate by humage.com
a.k.a.
Naked
Single by hodoku
One-Choice, or Sole Candidate, or Only Candidate, or Naked Single:
An empty square can only be filled with a number because all other numbers are taken in its row, column, or box.
Below is an example of using One-Choice(a.k.a. Sole Candidate, or Naked Single) to fill R1C1 (the square in the first row and the first column).
Very
Easy Sudoku on 03/13/2018
For the empty square R1C1 (the square in the first row and the first column), number 5 is its only choice because
- Numbers 1 and 2 show up in the first row where R1C1 is in.
- Number 3 already shows up in the first column where R1C1 is in.
- Number 4 already shows up in the first box where R1C1 is in.
- Numbers 6, 7, 8 show up in the first box where R1C1 is in.
- Number 9 shows up in the first row where R1C1 is in.
How to find them?
Scan the boxes (or rows, columns) which has many numbers filled.
When you see such a box, check every empty square in this box to
see whether it has only one candidate left. If it is, you can fill
this empty square with this only candidate.