Violation Prevention

In Violation Prevention, candidates that would violate the rules if placed in a cell are eliminated. For example, in Non-Consecutive Sudoku, a candidate that would force a neighboring cell to be consecutive is removed. Similarly, in Thermo Sudoku, a candidate that would break the ascending order of digits on a thermometer is eliminated.

Level: Medium

Let’s look at some examples:

Example 1

This puzzle includes the variants: Classic Sudoku, Non-consecutive, and Thermo.

Violation Prevention: The digit 7 can be eliminated from B9.

Why?

• B9 is the first cell on a three-cell thermo line.
• If B9 = 7, then B8 = 8 and B7 = 9.
• The digits 7, 8, and 9 would be next to each other, which violates the Non-consecutive rule.

Example 2

This puzzle includes the variants: Classic Sudoku, Killer, and Thermo.

Violation Prevention: The digit 4 can be eliminated from A5.

Why?

• A5 is the fourth cell on a four-cell thermo line.
• If A5 = 4, then B4 = 3.
• B4 is part of a Killer cage of three cells with a total sum of 21.
• There is no valid combination for this cage that includes the digit 3.

Possible combinations for 21: 489, 579, 678

Example 3

This puzzle includes the variants: Classic Sudoku, Non-consecutive, and Palindrome.

Violation Prevention: The digit 8 can be eliminated from A3.

Why?

• If A3 = 8, then A2 must be 7 or 9.
• Both 7 and 9 are consecutive to 8, which violates the Non-consecutive rule.