This means that square i3 is the only place left for 1. However, square g4 also contains 1, so no additional 1 is allowed in column g.

In this example, row 1 and row 2 contain 1s, which leaves two empty squares in the bottom of box 3. The same technique can be expanded by using information from perpendicular rows and columns. This leaves square e1 as the only possible place into which 9 can fit in. Looking at box 1 and box 3 we can see there are already 9s in row 2 and in row 3, which excludes the two bottom rows of box 2 from having 9. In our first example we will focus on box 2, which like any other box in Sudoku must contain 9. Here are some ways of using scanning techniques: 1. The scanning technique is also very useful for hard puzzles up to the point where no further progress can be made and more advanced solving techniques are required. The scanning technique is fast and usually sufficient to solve easy puzzles all the way to the end. The easiest way starting a Sudoku puzzle is to scan rows and columns within each triple-box area, eliminating numbers or squares and finding situations where only a single number can fit into a single square. The grid is also divided into nine 3x3 sub-grids named boxes which are marked box 1 through box 9.

Sudoku grid consists of 81 squares divided into nine columns marked a through i, and nine rows marked 1 through 9.

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