## Uniqueness: some simple exercises

Advanced methods and approaches for solving Sudoku puzzles

### Uniqueness: some simple exercises

In this post I present several puzzles that can be used as simple exercises by those who are studying Uniqueness for the first time and want to apply the more basic “versions” of this technique. The purpose of these exercises is to solve the grids using only Uniqueness (besides hidden and naked singles and pairs, but nothing beyond that).

Exercise 1:

Code: Select all
` *-----------------------* | 7 . . | . . . | . 1 9 | | 4 6 . | 1 9 . | . . . | | . . . | 6 8 2 | 7 . 4 | |-------+-------+-------| | . 9 . | . . . | . . 7 | | . . . | 3 . . | 4 . 5 | | . . 6 | 7 . . | . . . | |-------+-------+-------| | . . 1 | . . . | . . . | | 2 . . | . 7 4 | . . . | | . . . | 2 . . | 3 . . | *-----------------------*`

Exercise 2:

Code: Select all
` *-----------------------* | 4 . 1 | . 6 . | . . . | | 3 . . | . . . | 2 . . | | . . . | . . . | 8 . . | |-------+-------+-------| | 1 5 . | 2 . . | . . . | | 6 . . | . . . | . 1 . | | . . . | 9 . . | . . . | |-------+-------+-------| | . 2 . | 7 . 8 | . . . | | . . . | . . . | . 4 3 | | . 7 . | . . . | . . . | *-----------------------*`

Exercise 3:

Code: Select all
` *-----------------------* | . . . | . . . | 1 . 9 | | 4 . . | . 5 . | . . . | | . . . | . 2 . | 3 . . | |-------+-------+-------| | . . . | 1 . 9 | . . . | | 5 . . | . . 7 | . . . | | . . . | 3 . . | . . . | |-------+-------+-------| | . 1 3 | . . . | . . . | | . 8 . | . . . | . 4 . | | . . 9 | . . . | . 2 . | *-----------------------*`

Exercise 4:

Code: Select all
` *-----------------------* | 9 3 6 | . . . | . 7 5 | | 8 7 5 | . . 3 | . . 1 | | 1 4 2 | 7 5 6 | 3 8 9 | |-------+-------+-------| | . . 7 | . . . | 8 . . | | 5 1 4 | 8 . 2 | 7 . 6 | | . 8 9 | . 7 . | . . . | |-------+-------+-------| | 4 . . | . . 7 | 9 . 3 | | . . . | . 4 . | . . 7 | | 7 9 . | 2 . 5 | . . 8 | *-----------------------*`

Exercise 5:

Code: Select all
` *-----------------------* | . 7 8 | . . . | . 1 . | | 5 . . | . 4 . | . . . | | . . 6 | . 7 2 | . . . | |-------+-------+-------| | 8 5 . | . . . | . . . | | . . 4 | 5 . 7 | 9 . . | | . . . | . . . | . 6 4 | |-------+-------+-------| | . . . | 1 8 . | 2 . . | | . . . | . 6 . | . . 1 | | . 1 . | . . . | 3 5 . | *-----------------------*`

Exercise 6:

Code: Select all
` *-----------------------* | 8 9 6 | . 4 . | . . . | | . . . | . . . | 7 . 2 | | . . . | 9 . . | . 6 . | |-------+-------+-------| | . 1 8 | . . 9 | . 2 4 | | 6 . . | 3 . . | . 8 . | | . 3 . | . 1 . | . . . | |-------+-------+-------| | . . . | 4 . . | 2 . . | | 3 . . | . . 6 | . . . | | . . 5 | . 3 . | . 1 . | *-----------------------*`

Exercise 7 (2,+):

Code: Select all
` *-----------------------* | 3 . 1 | . . 5 | . . . | | . 2 . | 7 1 . | . . . | | . . 9 | 3 6 . | . 1 4 | |-------+-------+-------| | 7 1 8 | 5 3 . | 9 . 2 | | 6 . . | 2 9 1 | . . 8 | | 2 9 5 | . 8 7 | . . 1 | |-------+-------+-------| | 9 8 . | . 7 . | 1 . . | | 1 . . | . 5 3 | . 2 . | | . . . | 1 2 . | . . 6 | *-----------------------*`

Exercise 8 (1,+++):

Code: Select all
` *-----------------------* | . . . | . 7 . | . 8 6 | | . 2 . | 5 . . | . . . | | . . . | . . . | . . . | |-------+-------+-------| | . . . | . 6 3 | . . 7 | | . 5 . | . . . | 3 . . | | . . . | . 1 . | . . . | |-------+-------+-------| | . . . | 4 . . | 2 5 . | | 6 . . | 2 . . | . . . | | 1 . . | . . . | . . . | *-----------------------*`

Have fun.

Carcul
Last edited by Carcul on Fri Nov 17, 2006 6:49 am, edited 9 times in total.
Carcul

Posts: 724
Joined: 04 November 2005

Good examples Carcul. I got the Type 1 and Type 4 in the second exercise but I'd put a stupid artifical limit on my algorithm which stopped me seeing all the URs in exercise 1. Wound't have found that in a month of sundays. Nice one
AndrewStuart

Posts: 21
Joined: 28 December 2005

AndrewStuart wrote:Good examples Carcul.

Thanks.

Regards, Carcul
Carcul

Posts: 724
Joined: 04 November 2005