Hidden Set Sudoku — Hidden Pairs, Triples & Quads

If 2-4 in a are constrained to the same number of Cells, you've found a Hidden Set! We can safely remove other from the Cells.

How it works

Notice this row

These Cells are the only ones that can be a 7 or 9.

Only two spots left

We know the Row must eventually contain 7 and 9, and these are the only spots left. We can be certain these Cells can't be anything else.

Remove the other candidates

We can safely remove other from these Cells.

Let's look at a larger Hidden Set

In this , these Cells are the only ones that can be a 3, 7, or 9.

Only three spots left

This must eventually contain 3, 7, and 9, and these are the only spots.We can be certain these Cells can't be anything else.

Remove the other candidates

We can safely remove other from these Cells.

3
1
9
7
4
2
5
8
6
7
6
2
8
5
3
1
9
4
8
4
5
9
6
1
2
3
2
3
7
4
3
8
3
7
8
2
3
7
8
9
6
3
9
5
1
1
6
5
1
3
6
7
8
1
3
1
3
7
8
9
7
9
3
6
9
4
2
2
9
1
3
6
5
1
3
4
7
3
6
8
9
2
3
1
3
6
1
2
3
8
4
7
5
5
2
8
6
8
4
2
7
9
7
9
2
6
1
3
1
6
7
4
1
3
1
2
3
5
8
2
6
9
Notice this row
These Cells are the only ones that can be a 7 or 9.
3
1
9
7
4
2
5
8
6
7
6
2
8
5
3
1
9
4
8
4
5
9
6
1
2
3
2
3
7
4
3
8
3
7
8
2
3
7
8
9
6
3
9
5
1
1
6
5
1
3
6
7
8
1
3
1
3
7
8
9
7
9
3
6
9
4
2
2
9
1
3
6
5
1
3
4
7
3
6
8
9
2
3
1
3
6
1
2
3
8
4
7
5
5
2
8
6
8
4
2
7
9
7
9
2
6
1
3
1
6
7
4
1
3
1
2
3
5
8
2
6
9
Only two spots left
We know the Row must eventually contain 7 and 9, and these are the only spots left. We can be certain these Cells can't be anything else.
3
1
9
7
4
2
5
8
6
7
6
2
8
5
3
1
9
4
8
4
5
9
6
1
2
3
2
3
7
4
3
8
3
7
8
2
3
7
8
9
6
3
9
5
1
1
6
5
1
3
6
7
8
1
3
1
3
7
8
9
7
9
3
6
9
4
2
2
9
1
3
6
5
1
3
4
7
3
6
8
9
2
3
1
3
6
1
2
3
8
4
7
5
5
2
8
6
8
4
2
7
9
7
9
2
6
1
3
1
6
7
4
1
3
1
2
3
5
8
2
6
9
Remove the other candidates
We can safely remove other from these Cells.
3
6
7
9
1
6
8
5
2
3
6
3
6
7
4
1
2
6
9
1
2
6
9
4
5
6
2
1
4
5
8
4
6
9
7
1
6
3
3
4
6
7
9
4
6
4
7
9
1
2
3
4
6
3
6
7
8
5
2
6
9
2
4
8
6
3
5
1
9
7
2
4
1
3
4
5
9
6
9
7
2
5
6
4
6
8
2
5
9
7
5
9
6
9
8
4
1
2
5
6
3
1
2
6
6
8
5
3
4
1
6
9
6
8
1
2
6
1
2
6
8
9
7
4
6
8
9
2
7
1
6
5
3
1
4
6
8
1
4
6
4
6
7
8
1
4
6
1
4
7
2
1
3
6
9
3
6
8
1
6
1
4
6
8
9
5
Let's look at a larger Hidden Set
In this , these Cells are the only ones that can be a 3, 7, or 9.
3
6
7
9
1
6
8
5
2
3
6
3
6
7
4
1
2
6
9
1
2
6
9
4
5
6
2
1
4
5
8
4
6
9
7
1
6
3
3
4
6
7
9
4
6
4
7
9
1
2
3
4
6
3
6
7
8
5
2
6
9
2
4
8
6
3
5
1
9
7
2
4
1
3
4
5
9
6
9
7
2
5
6
4
6
8
2
5
9
7
5
9
6
9
8
4
1
2
5
6
3
1
2
6
6
8
5
3
4
1
6
9
6
8
1
2
6
1
2
6
8
9
7
4
6
8
9
2
7
1
6
5
3
1
4
6
8
1
4
6
4
6
7
8
1
4
6
1
4
7
2
1
3
6
9
3
6
8
1
6
1
4
6
8
9
5
Only three spots left
This must eventually contain 3, 7, and 9, and these are the only spots.We can be certain these Cells can't be anything else.
3
6
7
9
1
6
8
5
2
3
6
3
6
7
4
1
2
6
9
1
2
6
9
4
5
6
2
1
4
5
8
4
6
9
7
1
6
3
3
4
6
7
9
4
6
4
7
9
1
2
3
4
6
3
6
7
8
5
2
6
9
2
4
8
6
3
5
1
9
7
2
4
1
3
4
5
9
6
9
7
2
5
6
4
6
8
2
5
9
7
5
9
6
9
8
4
1
2
5
6
3
1
2
6
6
8
5
3
4
1
6
9
6
8
1
2
6
1
2
6
8
9
7
4
6
8
9
2
7
1
6
5
3
1
4
6
8
1
4
6
4
6
7
8
1
4
6
1
4
7
2
1
3
6
9
3
6
8
1
6
1
4
6
8
9
5
Remove the other candidates
We can safely remove other from these Cells.

All Hints

Unlock hints to find
the Hidden Set on your board.

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