Sudoku Discussions: A little tip to help solve the puzzles

Sudoku Discussions: A little tip to help solve the puzzles: "First of all, I think of the game as being made up not only of nine rows and columns, but also three 'broad' rows and columns, 3x3 boxes, and little boxes I call 'entries'.

My first step is to examine broad columns from left to right, then broad rows from top to bottom.

Let's say we're looking at a broad column. The 'examination' involves looking at pairs of values that occur in the broad column. If the same number appears twice, that eliminates two broad rows in that broad column. It also restricts us to look at the narrow column that the other two values are _not_ in. If that column has only one empty space, the value goes there. If it has more than one, but the number occurs in enough of the rows crossing the column, the number can be placed uniquely. If neither of these is true, you only know the value has to go in that column.

Each time I can fill in a value, I look at the effect that has on the broad row in which it occurred. I follow this logic until I can't fill that value in anywhere else. Now, following this general scheme, you make (in a sense) one pass through the puzzle's broad columns and rows and you've filled in all the 'easy' values.

Now I look at the boxes that are most-filled-in (usually you'll have at least one box with five values filled in). I look at the values that are missing and see if any of them can occur in only one place in the box. I do the same for the most-filled-in rows and the most-filled-in columns. In particular, look for positions where a most-filled-in column crosses a most-filled-in row at a blank entry.

I will continue to add more insights here.