Well, you have established that the 7 for the first column must be in one of the two highlighted rows; not in any other squares in this column. Let’s say, there are 3 different cells with exactly 2 candidates (notes) each that are related to each other.

The goal is to fill the grid, so that each row, column, and 3x3 block contain all the digits from 1 to 9 without repeating. This hardest Sudoku puzzle is characterized by the fact that only a few numbers are shown in the Sudoku square, which consists of 9 small squares, where the cells are located 3x3. The swordfish is similar to the x-wing technique, but on a larger scale, with three rows and columns instead of two. Any cell that intersects both pincers can’t longer contain a candidate for digit Z, because the pivot means either of the pincers to contain this digit. If you like playing some seriously hard Sudoku, try the puzzles at the end of The Times Sudoku 6 book with some requiring the swordfish technique.is a partially solved Sudoku, using easy and medium difficulty solving techniques; no more squares can be solved using them. If you really like Super Fiendish, you will have to wait a little longer for The Times Sudoku 7 with 25 extremely hard Sudoku, many requiring x-wing or swordfish to complete. With many advanced techniques, the key is to spot patterns within your pencil marks to eliminate possibilities within other squares. The best way to solve the evil sudoku puzzle is to start with the blocks where there are more prearranged numbers. While it's totally fine to play sudoku intuitively on the easy levels, evil sudoku requires the knowledge of some strategies.

The correction function is also very useful, since due to the high level of complexity, it is necessary to make corrections more often. Whenever you solve a square, you must remove that number from the pencil marks in all other squares in the same row, column and block. Simple logic and basic knowledge of sudoku rules won’t cut it – you as a player should know advanced sudoku solving techniques and understand how to apply them in practice.To take notes, tap the notes button in the lower right corner, and then tap the numbers in the button bar. Look along each of the rows in turn, noting each one that contains only two or three squares with the current number as a possibility. Essentially, this method uses the fact that in certain cases, there are only two possible ways of placing two numbers in four squares which form a rectangle. Press N to switch to note-taking mode, or press Shift-1 through Shift-9 to set notes without switching modes. A swordfish is found when for three rows, there are two or three possible squares in which a particular number can be placed, and for all three rows these squares lie in the same three columns.