Killer Sudoku – Medium

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Killer Sudoku, also known by various other names such as "Sums Sudoku", "Sums Number Place", "Samunamupure", or "Kikagaku Nampure", is a variant of the classic Sudoku puzzle. In addition to adhering to the traditional Sudoku rules, it introduces a new layer of complexity by grouping cells into small areas, each labeled with a number that represents the sum of the numbers within that area.

Basic Rules

• The grid is a 9x9 square divided into smaller squares (3x3), just like classic Sudoku.
• Each row, column, and 3x3 square must contain the numbers 1 through 9, without repetition.
• Cells are grouped into cages, each with a specified sum. The numbers within each cage must add up to the given sum.

Additional Rules

• Numbers within a cage must also be unique.
• Some cells may not be part of any cage, and in such cases, only the standard Sudoku rules apply to them.

Basic Solving Tips

• Start with Certainties: Begin by filling in numbers that are certain, usually starting with cages that have the smallest sums or the fewest cells.
• Use Elimination: If a number appears in a row, column, or small square, eliminate it as a possibility from other cages intersecting with that area.
• Consider the Sums: Use the sums to your advantage. If a cage must sum to a certain number, consider which combinations of numbers can achieve that sum and use that to narrow down possibilities.
• Look for Exclusivity: Sometimes, a number or a sum may only be possible in one specific cage or cell. Identify these opportunities to make confident placements.
• Overlap Strategy: Focus on areas where cages overlap with rows, columns, or squares to find numbers that fit both the cage sum and Sudoku rules.