Platon Sudoku · Sudoku Study

Peers · Core Concepts

Two cells see each other when they share a row, column or 3×3 box.

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Definition

Two cells see each other when they share a row, column or 3×3 box.

How to find it

From one cell, check the other against its row, column and box.

Common mistake

Nearby or diagonal does not imply visibility. Cells in different boxes can still share a row or column.

All peers

Teaching board · local candidate diagram

Observe candidates

Start at reference cell r5c5; only positions matter, so no digits are needed.

r5c5 is the reference cell; the 20 marked other cells share row 5, column 5, box 5 with it, regardless of digits.

Verify the condition

The 20 marked cells share row 5, column 5, box 5 with the reference; exclude the reference itself and count overlaps only once.

r5c5 is the reference cell; the 20 marked other cells share row 5, column 5, box 5 with it, regardless of digits.

Draw the conclusion

These are the reference cell’s peers, with or without digits; placing a digit in the reference rules out that digit in every peer.

r5c5 is the reference cell; the 20 marked other cells share row 5, column 5, box 5 with it, regardless of digits.

Row

Teaching board · local candidate diagram

Observe candidates

Start at reference cell r2c2; only positions matter, so no digits are needed.

r2c2 is the reference cell; the 1 marked other cells share row 2 with it, regardless of digits.

Verify the condition

The 1 marked cells share row 2 with the reference; exclude the reference itself and count overlaps only once.

r2c2 is the reference cell; the 1 marked other cells share row 2 with it, regardless of digits.

Draw the conclusion

These are the reference cell’s peers, with or without digits; placing a digit in the reference rules out that digit in every peer.

r2c2 is the reference cell; the 1 marked other cells share row 2 with it, regardless of digits.

Column

Teaching board · local candidate diagram

Observe candidates

Start at reference cell r2c2; only positions matter, so no digits are needed.

r2c2 is the reference cell; the 1 marked other cells share column 2 with it, regardless of digits.

Verify the condition

The 1 marked cells share column 2 with the reference; exclude the reference itself and count overlaps only once.

r2c2 is the reference cell; the 1 marked other cells share column 2 with it, regardless of digits.

Draw the conclusion

These are the reference cell’s peers, with or without digits; placing a digit in the reference rules out that digit in every peer.

r2c2 is the reference cell; the 1 marked other cells share column 2 with it, regardless of digits.

Box

Teaching board · local candidate diagram

Observe candidates

Start at reference cell r2c2; only positions matter, so no digits are needed.

r2c2 is the reference cell; the 1 marked other cells share box 1 with it, regardless of digits.

Verify the condition

The 1 marked cells share box 1 with the reference; exclude the reference itself and count overlaps only once.

r2c2 is the reference cell; the 1 marked other cells share box 1 with it, regardless of digits.

Draw the conclusion

These are the reference cell’s peers, with or without digits; placing a digit in the reference rules out that digit in every peer.

r2c2 is the reference cell; the 1 marked other cells share box 1 with it, regardless of digits.