Sudoku Algorithms

According to Sudoku rules, each number should appear at list once in each box, row, and column. Hidden Single is a number that appears as a possible candidate only in one cell for the whole box, row, or column. In this case this number should go into the cell, since there are no other candidates. A picture on the left shows an example of Hidden Single in a box. The number '5' (marked green) in box (1*1) appears in the list of possible candidates only in cell A3. Number 5 is the solution for the cell A3.

A picture on the left shows an example of the Hidden Single in a row. The only possible candidate for the number '5' (marked green) in row I is in the cell I5. We should enter number 5 into the cell I5.

A picture on the left shows the Hidden Single in a column. Number '8' (marked green) in cell E1 is the only possible candidate 8 in column 1. We can enter number 8 into the cell E1.