Variant Sudoku

Odd Even Sudoku Explained in One Short Example

0:15 · Odd and even cells · Variant Sudoku

A four-cell row has a circle and a square. A 5 in the square breaks the rule because 5 is odd, and a 3 in the circle with a 4 in the square passes.

Full lesson and practiceFind Odd/Even puzzles

Transcript

  1. 0:02Gray circles hold odd digits. Gray squares hold even digits.
  2. 0:065 is odd, so it can’t go in a square.
  3. 0:093 in the circle, 4 in the square.

The rule

Odd-even sudoku marks some cells with shapes. A gray circle means the cell holds an odd digit, and a gray square means it holds an even digit. Normal sudoku rules still apply.

Each mark cuts a cell to five or four options before you start. The marks do the most work when you count how many odd and even cells are left in a row, column or box.

Worth memorizing

  1. There are five odd digits (1, 3, 5, 7, 9) and four even ones (2, 4, 6, 8).

  2. So a box can hold at most four squares, and five circles force every odd digit into them.

  3. Pair it with sums: an odd circle plus an even square always makes an odd total.

Practice odd and even cells in the lesson

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