perplexus.info :: Logic : No repeated numbers

No repeated numbers (Posted on 2008-08-20)

Look at the 8x8 grid below at left. In the rows and columns there are repeated numbers. Erasing 19 of them, we achieve the grid at right, that has no repeated numbers in any row, in any column.

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

Do the same with this 8x8 grid, erasing the minimum number of squares.

                    +---+---+---+---+---+---+---+---+
                    | 8 | 4 | 6 | 5 | 3 | 5 | 7 | 4 |
                    +---+---+---+---+---+---+---+---+
                    | 6 | 5 | 5 | 4 | 7 | 8 | 3 | 1 |
                    +---+---+---+---+---+---+---+---+ 
                    | 5 | 7 | 2 | 5 | 5 | 4 | 8 | 7 |
                    +---+---+---+---+---+---+---+---+
                    | 8 | 6 | 5 | 3 | 2 | 5 | 4 | 4 |
                    +---+---+---+---+---+---+---+---+
                    | 3 | 8 | 1 | 4 | 8 | 6 | 5 | 2 |
                    +---+---+---+---+---+---+---+---+ 
                    | 5 | 3 | 7 | 6 | 4 | 2 | 2 | 2 |
                    +---+---+---+---+---+---+---+---+
                    | 5 | 8 | 7 | 7 | 6 | 2 | 1 | 3 |
                    +---+---+---+---+---+---+---+---+
                    | 1 | 1 | 3 | 7 | 6 | 4 | 6 | 8 |
                    +---+---+---+---+---+---+---+---+

See The Solution Submitted by pcbouhid

Rating: 4.0000 (3 votes)

Comments: ( You must be logged in to post comments.)

Subject	Author	Date
answer this post	PittmanBetty	2011-10-22 09:01:08
reply this post	ArleneFOX19	2011-10-22 06:38:29
2880 solutions; 6 Hitori	Charlie	2008-08-24 13:10:41
re(5): ===== so, you beat them?	Steve Herman	2008-08-24 08:25:46
Computer solution at last	Charlie	2008-08-23 17:11:48
re: A look at minimality	Charlie	2008-08-22 10:51:57
A look at minimality	Gamer	2008-08-21 17:04:55
re(4): ===== so, you beat them? (Spoiler)	pcbouhid	2008-08-21 12:36:46
re(3): ===== so, you beat them? (Spoiler)	Dej Mar	2008-08-21 09:56:29
re(2): ===== so, you beat them?	pcbouhid	2008-08-21 08:39:31
re:	brianjn	2008-08-21 00:28:09
optimal algarithm (no proof)	Daniel	2008-08-21 00:12:55
re: "HITORI"	Dej Mar	2008-08-21 00:10:25
Cross Referencing	brianjn	2008-08-20 23:40:54
"HITORI"	pcbouhid	2008-08-20 22:09:27
Now, can we prove this is minimal?	ed bottemiller	2008-08-20 17:13:26
A solution	Dej Mar	2008-08-20 17:00:30
Those Fives!	ed bottemiller	2008-08-20 16:47:05
As a Start...	ed bottemiller	2008-08-20 16:20:19
possible solution (spoiler)	Daniel	2008-08-20 15:35:42

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