Platon Games
English

Platon Sudoku · Sudoku Study

Locked Candidates · Claiming · Step-by-step example

All possible places for one digit in a row or column lie inside the same box. Remove that digit from other cells in the box, outside the selected row or column.

This course is adapted from Platon Sudoku App. Read the complete example here, then continue learning and practising in the app.

View on Google Play

Recognize the pattern

All possible places for one digit in a row or column lie inside the same box.

How to find it

Choose a digit and scan a row or column. Check whether its remaining positions all fall in one box.

What it allows

Remove that digit from other cells in the box, outside the selected row or column.

Avoid the mix-up

The selected line must have no possible place for that digit in another box. Pointing starts from a box and removes candidates along a line outside it.

Step-by-step example · Row

This example starts from a saved intermediate position. Its candidates include earlier logical eliminations; they are not fresh automatic notes.

Blue: evidence. Green: conclusion. Crossed-out digits: eliminated candidates. R1C1 means row 1, column 1.

Step 1 · Where to look

In row 4, 4 can go only in R4C7, R4C8. The digit must appear once in this region.

In row 4, 4 can go only in R4C7, R4C8. The digit must appear once in this region.
In row 4, 4 can go only in R4C7, R4C8. The digit must appear once in this region.
Step 2 · Lock the digit into the intersection

All positions in row 4 lie in box 6. Since row 4 must contain 4, the intersection supplies it. Other cells in box 6 cannot contain 4.

All positions in row 4 lie in box 6. Since row 4 must contain 4, the intersection supplies it. Other cells in box 6 cannot contain 4.
All positions in row 4 lie in box 6. Since row 4 must contain 4, the intersection supplies it. Other cells in box 6 cannot contain 4.
Step 3 · Conclusion

The 4 in row 4 must lie in box 6. Therefore the targets in box 6 but outside row 4 cannot be 4: R5C7=4, R6C7=4.

The 4 in row 4 must lie in box 6. Therefore the targets in box 6 but outside row 4 cannot be 4: R5C7=4, R6C7=4.
The 4 in row 4 must lie in box 6. Therefore the targets in box 6 but outside row 4 cannot be 4: R5C7=4, R6C7=4.

What it allows

The 4 in row 4 must lie in box 6. Therefore the targets in box 6 but outside row 4 cannot be 4: R5C7=4, R6C7=4.

Locked Candidates · Claiming · Remove that digit from other cells in the box, outside the selected row or column.
Locked Candidates · Claiming · Remove that digit from other cells in the box, outside the selected row or column.

Step-by-step example · Column

This example starts from a saved intermediate position. Its candidates include earlier logical eliminations; they are not fresh automatic notes.

Blue: evidence. Green: conclusion. Crossed-out digits: eliminated candidates. R1C1 means row 1, column 1.

Step 1 · Where to look

In column 6, 1 can go only in R4C6, R6C6. The digit must appear once in this region.

In column 6, 1 can go only in R4C6, R6C6. The digit must appear once in this region.
In column 6, 1 can go only in R4C6, R6C6. The digit must appear once in this region.
Step 2 · Lock the digit into the intersection

All positions in column 6 lie in box 5. Since column 6 must contain 1, the intersection supplies it. Other cells in box 5 cannot contain 1.

All positions in column 6 lie in box 5. Since column 6 must contain 1, the intersection supplies it. Other cells in box 5 cannot contain 1.
All positions in column 6 lie in box 5. Since column 6 must contain 1, the intersection supplies it. Other cells in box 5 cannot contain 1.
Step 3 · Conclusion

The 1 in column 6 must lie in box 5. Therefore the targets in box 5 but outside column 6 cannot be 1: R4C4=1, R6C4=1.

The 1 in column 6 must lie in box 5. Therefore the targets in box 5 but outside column 6 cannot be 1: R4C4=1, R6C4=1.
The 1 in column 6 must lie in box 5. Therefore the targets in box 5 but outside column 6 cannot be 1: R4C4=1, R6C4=1.

What it allows

The 1 in column 6 must lie in box 5. Therefore the targets in box 5 but outside column 6 cannot be 1: R4C4=1, R6C4=1.

Locked Candidates · Claiming · Remove that digit from other cells in the box, outside the selected row or column.
Locked Candidates · Claiming · Remove that digit from other cells in the box, outside the selected row or column.

Practice

This course is adapted from Platon Sudoku App. Read the complete example here, then continue learning and practising in the app.

View on Google Play