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Platon Sudoku · Sudoku Study

Hidden sets · Core Concepts

In one region, N digits occur in only N cells, even if those cells contain other notes.

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

Definition

In one region, N digits occur in only N cells, even if those cells contain other notes.

How to find it

Choose the digits and count every place they can occupy across the whole region.

Common mistake

Check the whole region. A selected digit outside the highlighted cells breaks this hidden set.

Pair · Row

Teaching board · local candidate diagram

Observe candidates

In one region, N digits occur in only N cells, even if those cells contain other notes.

In row 2, 2, 3 can occupy only the 2 marked cells, even though other notes are present.
In row 2, 2, 3 can occupy only the 2 marked cells, even though other notes are present.
Verify the condition

Choose the digits and count every place they can occupy across the whole region.

In row 2, 2, 3 can occupy only the 2 marked cells, even though other notes are present.
In row 2, 2, 3 can occupy only the 2 marked cells, even though other notes are present.
Draw the conclusion

The selected digits occur only in the marked cells of this region: a hidden set.

In row 2, 2, 3 can occupy only the 2 marked cells, even though other notes are present.
In row 2, 2, 3 can occupy only the 2 marked cells, even though other notes are present.

Pair · Column

Teaching board · local candidate diagram

Observe candidates

In one region, N digits occur in only N cells, even if those cells contain other notes.

In column 2, 2, 3 can occupy only the 2 marked cells, even though other notes are present.
In column 2, 2, 3 can occupy only the 2 marked cells, even though other notes are present.
Verify the condition

Choose the digits and count every place they can occupy across the whole region.

In column 2, 2, 3 can occupy only the 2 marked cells, even though other notes are present.
In column 2, 2, 3 can occupy only the 2 marked cells, even though other notes are present.
Draw the conclusion

The selected digits occur only in the marked cells of this region: a hidden set.

In column 2, 2, 3 can occupy only the 2 marked cells, even though other notes are present.
In column 2, 2, 3 can occupy only the 2 marked cells, even though other notes are present.

Pair · Box

Teaching board · local candidate diagram

Observe candidates

In one region, N digits occur in only N cells, even if those cells contain other notes.

In box 1, 2, 3 can occupy only the 2 marked cells, even though other notes are present.
In box 1, 2, 3 can occupy only the 2 marked cells, even though other notes are present.
Verify the condition

Choose the digits and count every place they can occupy across the whole region.

In box 1, 2, 3 can occupy only the 2 marked cells, even though other notes are present.
In box 1, 2, 3 can occupy only the 2 marked cells, even though other notes are present.
Draw the conclusion

The selected digits occur only in the marked cells of this region: a hidden set.

In box 1, 2, 3 can occupy only the 2 marked cells, even though other notes are present.
In box 1, 2, 3 can occupy only the 2 marked cells, even though other notes are present.

Triple · Row

Teaching board · local candidate diagram

Observe candidates

In one region, N digits occur in only N cells, even if those cells contain other notes.

In row 2, 2, 3, 4 can occupy only the 3 marked cells, even though other notes are present.
In row 2, 2, 3, 4 can occupy only the 3 marked cells, even though other notes are present.
Verify the condition

Choose the digits and count every place they can occupy across the whole region.

In row 2, 2, 3, 4 can occupy only the 3 marked cells, even though other notes are present.
In row 2, 2, 3, 4 can occupy only the 3 marked cells, even though other notes are present.
Draw the conclusion

The selected digits occur only in the marked cells of this region: a hidden set.

In row 2, 2, 3, 4 can occupy only the 3 marked cells, even though other notes are present.
In row 2, 2, 3, 4 can occupy only the 3 marked cells, even though other notes are present.

Triple · Column

Teaching board · local candidate diagram

Observe candidates

In one region, N digits occur in only N cells, even if those cells contain other notes.

In column 2, 2, 3, 4 can occupy only the 3 marked cells, even though other notes are present.
In column 2, 2, 3, 4 can occupy only the 3 marked cells, even though other notes are present.
Verify the condition

Choose the digits and count every place they can occupy across the whole region.

In column 2, 2, 3, 4 can occupy only the 3 marked cells, even though other notes are present.
In column 2, 2, 3, 4 can occupy only the 3 marked cells, even though other notes are present.
Draw the conclusion

The selected digits occur only in the marked cells of this region: a hidden set.

In column 2, 2, 3, 4 can occupy only the 3 marked cells, even though other notes are present.
In column 2, 2, 3, 4 can occupy only the 3 marked cells, even though other notes are present.

Triple · Box

Teaching board · local candidate diagram

Observe candidates

In one region, N digits occur in only N cells, even if those cells contain other notes.

In box 1, 2, 3, 4 can occupy only the 3 marked cells, even though other notes are present.
In box 1, 2, 3, 4 can occupy only the 3 marked cells, even though other notes are present.
Verify the condition

Choose the digits and count every place they can occupy across the whole region.

In box 1, 2, 3, 4 can occupy only the 3 marked cells, even though other notes are present.
In box 1, 2, 3, 4 can occupy only the 3 marked cells, even though other notes are present.
Draw the conclusion

The selected digits occur only in the marked cells of this region: a hidden set.

In box 1, 2, 3, 4 can occupy only the 3 marked cells, even though other notes are present.
In box 1, 2, 3, 4 can occupy only the 3 marked cells, even though other notes are present.

Quad · Row

Teaching board · local candidate diagram

Observe candidates

In one region, N digits occur in only N cells, even if those cells contain other notes.

In row 2, 2, 3, 4, 5 can occupy only the 4 marked cells, even though other notes are present.
In row 2, 2, 3, 4, 5 can occupy only the 4 marked cells, even though other notes are present.
Verify the condition

Choose the digits and count every place they can occupy across the whole region.

In row 2, 2, 3, 4, 5 can occupy only the 4 marked cells, even though other notes are present.
In row 2, 2, 3, 4, 5 can occupy only the 4 marked cells, even though other notes are present.
Draw the conclusion

The selected digits occur only in the marked cells of this region: a hidden set.

In row 2, 2, 3, 4, 5 can occupy only the 4 marked cells, even though other notes are present.
In row 2, 2, 3, 4, 5 can occupy only the 4 marked cells, even though other notes are present.

Quad · Column

Teaching board · local candidate diagram

Observe candidates

In one region, N digits occur in only N cells, even if those cells contain other notes.

In column 2, 2, 3, 4, 5 can occupy only the 4 marked cells, even though other notes are present.
In column 2, 2, 3, 4, 5 can occupy only the 4 marked cells, even though other notes are present.
Verify the condition

Choose the digits and count every place they can occupy across the whole region.

In column 2, 2, 3, 4, 5 can occupy only the 4 marked cells, even though other notes are present.
In column 2, 2, 3, 4, 5 can occupy only the 4 marked cells, even though other notes are present.
Draw the conclusion

The selected digits occur only in the marked cells of this region: a hidden set.

In column 2, 2, 3, 4, 5 can occupy only the 4 marked cells, even though other notes are present.
In column 2, 2, 3, 4, 5 can occupy only the 4 marked cells, even though other notes are present.

Quad · Box

Teaching board · local candidate diagram

Observe candidates

In one region, N digits occur in only N cells, even if those cells contain other notes.

In box 1, 2, 3, 4, 5 can occupy only the 4 marked cells, even though other notes are present.
In box 1, 2, 3, 4, 5 can occupy only the 4 marked cells, even though other notes are present.
Verify the condition

Choose the digits and count every place they can occupy across the whole region.

In box 1, 2, 3, 4, 5 can occupy only the 4 marked cells, even though other notes are present.
In box 1, 2, 3, 4, 5 can occupy only the 4 marked cells, even though other notes are present.
Draw the conclusion

The selected digits occur only in the marked cells of this region: a hidden set.

In box 1, 2, 3, 4, 5 can occupy only the 4 marked cells, even though other notes are present.
In box 1, 2, 3, 4, 5 can occupy only the 4 marked cells, even though other notes are present.

Recognition practice

Teaching board · local candidate diagram

Recognition practice 1

Do the highlighted digits form a hidden set in the marked region?

Teaching board · local candidate diagram
Teaching board · local candidate diagram
Draw the conclusion

Yes

Recognition practice 2

Do the highlighted digits form a hidden set in the marked region?

Teaching board · local candidate diagram
Teaching board · local candidate diagram
Draw the conclusion

No

Recognition practice 3

Do the highlighted digits form a hidden set in the marked region?

Teaching board · local candidate diagram
Teaching board · local candidate diagram
Draw the conclusion

Yes

Recognition practice 4

Do the highlighted digits form a hidden set in the marked region?

Teaching board · local candidate diagram
Teaching board · local candidate diagram
Draw the conclusion

No

Recognition practice 5

Do the highlighted digits form a hidden set in the marked region?

Teaching board · local candidate diagram
Teaching board · local candidate diagram
Draw the conclusion

Yes

Recognition practice 6

Do the highlighted digits form a hidden set in the marked region?

Teaching board · local candidate diagram
Teaching board · local candidate diagram
Draw the conclusion

No

Recognition practice 7

Do the highlighted digits form a hidden set in the marked region?

Teaching board · local candidate diagram
Teaching board · local candidate diagram
Draw the conclusion

Yes

Recognition practice 8

Do the highlighted digits form a hidden set in the marked region?

Teaching board · local candidate diagram
Teaching board · local candidate diagram
Draw the conclusion

No

Recognition practice 9

Do the highlighted digits form a hidden set in the marked region?

Teaching board · local candidate diagram
Teaching board · local candidate diagram
Draw the conclusion

Yes

Recognition practice 10

Do the highlighted digits form a hidden set in the marked region?

Teaching board · local candidate diagram
Teaching board · local candidate diagram
Draw the conclusion

No

Recognition practice 11

Do the highlighted digits form a hidden set in the marked region?

Teaching board · local candidate diagram
Teaching board · local candidate diagram
Draw the conclusion

Yes

Recognition practice 12

Do the highlighted digits form a hidden set in the marked region?

Teaching board · local candidate diagram
Teaching board · local candidate diagram
Draw the conclusion

No

Recognition practice 13

Do the highlighted digits form a hidden set in the marked region?

Teaching board · local candidate diagram
Teaching board · local candidate diagram
Draw the conclusion

Yes

Recognition practice 14

Do the highlighted digits form a hidden set in the marked region?

Teaching board · local candidate diagram
Teaching board · local candidate diagram
Draw the conclusion

No

Recognition practice 15

Do the highlighted digits form a hidden set in the marked region?

Teaching board · local candidate diagram
Teaching board · local candidate diagram
Draw the conclusion

Yes

Recognition practice 16

Do the highlighted digits form a hidden set in the marked region?

Teaching board · local candidate diagram
Teaching board · local candidate diagram
Draw the conclusion

No

Recognition practice 17

Do the highlighted digits form a hidden set in the marked region?

Teaching board · local candidate diagram
Teaching board · local candidate diagram
Draw the conclusion

Yes

Recognition practice 18

Do the highlighted digits form a hidden set in the marked region?

Teaching board · local candidate diagram
Teaching board · local candidate diagram
Draw the conclusion

No

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