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Hidden Singles

  If a number only shows up as a candidate in one cell of a row or column, you may set that cell value to be that number. In the example below the candidate 7 is only found in C7 along the highlighted row. Since each row must contain one 7, this cell must be the 7. This is a hidden single and is given a Sudoku Snake skill value of 3.

  Like with hidden singles by box, this technique can be spotted without filling in the candidates by visualizing the elimination of units and seeing what remains. The above example is repeated below in this manner. By visualizing the elimination of the shown columns and box, it can be seen that a 7 must go in the green cell.

Elders of Genova
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