Killer sudoku 4x4

Killer Sudoku Rules

• Fill the numbers 1-9 into each row, column, and 3x3 subgrid of a 9x9 grid.

• Each number can only appear once in each row, column, and 3x3 subgrid.

• Fill in the blank cells with the numbers 1-9 so that each row, column, and 3x3 subgrid contains the numbers 1-9.

• There are also "killer cells" in the grid. These cells contain a range of numbers, and the sum of the numbers in each killer cell must be equal to the number in the cell.

In four-cell Killer Sudoku, there is a "10" rule. In six-cell Killer Sudoku, there is a "21" rule. Similarly, in nine-cell Killer Sudoku, there is a "45" rule.

The "45" rule: Since the sum of the numbers in each row, column, and region is equal to 45, the "45" rule is the most basic, most common, and most effective weapon for solving nine-cell Killer Sudoku.