single candidate strategy for solving sudoku
Basic strategies
Single candidate (Lone number)
After writing candidates, this strategy is really simple to use. While I recommend using pencil marks for this strategy, more experienced solvers are quite capable of doing this in their head.
We have to look for the lone number. Principle is if there is only one place for a number to go, then it is true for that block, and also the line and column it is in. You can therefore eliminate all the other candidates in the block, line and column.
Example
In this example, all the options for middle block have been marked with candidates. There are two cells where the number 8 might go.
But look, there is a lone number “8”. As no other number can go in that cell, we have to place the “8” in the left yellow cell.
List of methods
