Mirrored from Sudopedia, the Free Sudoku Reference Guide

# Valid Test Cases

These test cases should result in a valid puzzle, and potentially a unique solution.

## Completed Puzzle

A case of ‘more than enough’, this puzzle has already been solved. Nonetheless, it is still a valid puzzle, and should be parsed successfully.

Givens

```9 7 4 | 2 3 6 | 1 5 8
6 3 8 | 5 9 1 | 7 4 2
1 2 5 | 4 8 7 | 9 3 6
------+-------+------
3 1 6 | 7 5 4 | 2 8 9
7 4 2 | 9 1 8 | 5 6 3
5 8 9 | 3 6 2 | 4 1 7
------+-------+------
8 6 7 | 1 2 5 | 3 9 4
2 5 3 | 6 4 9 | 8 7 1
4 9 1 | 8 7 3 | 6 2 5
```
```974236158638591742125487936316754289742918563589362417867125394253649871491873625
```

Solution

```974236158638591742125487936316754289742918563589362417867125394253649871491873625
```

Pass Condition

Unique Solution Found

## Last Empty Square

This puzzle requires only a single value to be placed on the grid in order to reach the unique solution: a ‘3’ in square r5c5.

Givens

```2 5 6 | 4 8 9 | 1 7 3
3 7 4 | 6 1 5 | 9 8 2
9 8 1 | 7 2 3 | 4 5 6
------+-------+------
5 9 3 | 2 7 4 | 8 6 1
7 1 2 | 8 . 6 | 5 4 9
4 6 8 | 5 9 1 | 3 2 7
------+-------+------
6 3 5 | 1 4 7 | 2 9 8
1 2 7 | 9 5 8 | 6 3 4
8 4 9 | 3 6 2 | 7 1 5
```
```2564891733746159829817234565932748617128.6549468591327635147298127958634849362715
```

Solution

```256489173374615982981723456593274861712836549468591327635147298127958634849362715
```

Pass Condition

Unique Solution Found

## Naked Singles

This puzzle can be solved using only ‘Naked Singles’—also called ‘sole candidates’—which occur when a square has only one possible value remaining. The most obvious example of a Naked Single is the last square in any box, column, or row.

Givens

```3 . 5 | 4 2 . | 8 1 .
4 8 7 | 9 . 1 | 5 . 6
. 2 9 | . 5 6 | 3 7 4
------+-------+------
8 5 . | 7 9 3 | . 4 1
6 1 3 | 2 . 8 | 9 5 7
. 7 4 | . 6 5 | 2 8 .
------+-------+------
2 4 1 | 3 . 9 | . 6 5
5 . 8 | 6 7 . | 1 9 2
. 9 6 | 5 1 2 | 4 . 8
```
```3.542.81.4879.15.6.29.5637485.793.416132.8957.74.6528.2413.9.655.867.192.965124.8
```

Solution

```365427819487931526129856374852793641613248957974165283241389765538674192796512438
```

Pass Condition

Unique Solution

Naked Singles:

```r1c2 => 6	r1c6 => 7	r1c9 => 9	r2c5 => 3
r2c8 => 2	r3c1 => 1	r3c4 => 8	r4c3 => 2
r4c7 => 6	r5c5 => 4	r6c1 => 9	r6c4 => 1
r6c9 => 3	r7c5 => 8	r7c7 => 7	r8c2 => 3
r8c6 => 4	r9c1 => 7	r9c8 => 3
```

## Hidden Singles

This puzzle requires ‘Hidden Singles’ to solve, which occur when a box, column, or row has only one possible square remaining for a given value.

Givens

```. . 2 | . 3 . | . . 8
. . . | . . 8 | . . .
. 3 1 | . 2 . | . . .
------+-------+------
. 6 . | . 5 . | 2 7 .
. 1 . | . . . | . 5 .
2 . 4 | . 6 . | . 3 1
------+-------+------
. . . | . 8 . | 6 . 5
. . . | . . . | . 1 3
. . 5 | 3 1 . | 4 . .
```
```..2.3...8.....8....31.2.....6..5.27..1.....5.2.4.6..31....8.6.5.......13..531.4..
```

Solution

```672435198549178362831629547368951274917243856254867931193784625486592713725316489
```

Pass Condition

Unique Solution

Hidden Singles:

```r3c1 => 8	r7c1 => 1	r2c7 => 3	r2c4 => 1
r1c7 => 1	r3c7 => 5	r6c2 => 5	r2c1 => 5
r4c6 => 1	r5c6 => 3	r4c1 => 3	r7c3 => 3
r5c4 => 2	r5c9 => 6	r5c5 => 4	r4c9 => 4
r8c7 => 7
```