The New Sudoku Players' Forum

[999_Springs]

well I never thought I'd have to revisit these forums again but...

so lately i've been getting back into killer sudokus from the times (uk newspaper) mainly out of boredom (after several unsuccessful attempts at landing a summer job... ugggghhh) and either i've got rusty or some of these have got a lot harder. i can usually whip out solutions, but these two have me seriously stumped.

#3206 - tough (26 min)

Code: Select all

+--+-----+--+-----+--+-----+
|23|6    |13|20   |7 |10   |
|  +--+--+  |  +--+  |  +--+
|     |     |  |21|  |  |14|
+-----+--+--+--+  +--+--+  |
|12   |13|17|     |22|11|  |
|  +--+  |  |  +--+  |  +--+
|  |14|  |  |  |11|  |  |12|
+--+  +--+  +--+  |  +--+  |
|     |        |  |  |11|  |
|  +--+-----+--+--+--+  +--+
|  |17|17   |14|4    |  |3 |
+--+  +--+--+  +-----+--+  |
|16|     |     |24   |21|  |
|  +--+--+--+--+     |  +--+
|  |13|18   |13|     |     |
|  |  |     |  +-----+-----+
|  |  |     |        |8    |
+--+--+-----+--------+-----+

all I've got is r6c6=3, r6c7=1, r6c9=2, r7c9=1 (all easy), a 46 pair in r6c25, and a 57 pair in r6c18. apart from that, all i've got are the obvious cage sums.

#3223 - deadly (56 min)

Code: Select all

+--+--------+-----------+--+
|32|15      |34         |11|
|  +--+  +--+-----+     |  |
|     |  |24      |     |  |
+--+  |  +-----+  +-----+--+
|17|  |  |21   |  |31   |21|
|  |  +--+     +--+     |  |
|  |  |           |     |  |
|  +--+-----+-----+     |  |
|     |17   |24   |     |  |
+--+--+--+  +--+  +--+--+--+
|19|24   |     |     |10   |
|  |     +-----+-----+     |
|  |     |26         |     |
|  |  +--+--+--------+-----+
|  |  |28   |10      |12   |
+--+--+     +--------+-----+
|7    |     |12      |10   |
+-----+-----+--------+-----+

this one looks completely intractable...apart from the obvious cage sums like 10/4, 15/5, 21/6, 32/5 (as well as the 11/2 and 21/3 in column 9) must have 8 and 9 in it, and 34/6 must have 9 in it, i can split the 28/4 into a 48 pair at the top and 79 at the bottom. that's it.

by the way, PLEASE NO COPY AND PASTED SOLVER OUTPUT. i'm enjoying doing these manually and i think it would be much more fun for you to enjoy the challenge of doing these monsters by hand.

/re-necrocomeback

[SCLT]

I've just finished solving the Deadly puzzle - it wasn't too bad with a large hand-drawn grid and proper pencil-marking. A full step-by-step of what I did, in hidden text. Follow in as far as you feel like - all the way if you don't care too much about solving it, or a little way in if you want a small hint.

Hidden Text: Show

To start, assume all cells can take all values

10 cage in r6/7 must be 1,2,3,4 - eliminate 5/6/7/8/9

15 cage in r1/2/3 must be 1,2,3,4,5 - eliminate 6/7/8/9

21 cage in r3/4 must be 1,2,3,4,5,6 - eliminate 7/8/9

32 cage in c1/2 cannot contain a 1 - eliminate it

11 cage in c9 cannot contain a 1 - eliminate it

21 cage in c9 cannot contain 1/2/3 - eliminate them

19 cage in c1 cannot contain a 1 - eliminate it

26 cage in r7 cannot contain a 1 - eliminate it

7 cage in r9 cannot contain 7/8/9 - eliminate them

12 cage in r8 cannot contain 1/2 - eliminate them

7,12 and 10 cages in r9 sum to 29, leaving the remaining two cells to make 16. This must be 7,9, so eliminate 1/2/3/4/5/6/8 from these two cells

Naked pair of 7/9 in r9

Remaining two cells of 28 cage sum to 12 - must be 4,8, so eliminate 1/2/3/5/6/7/9

Naked pair of 4/8 in r8

10 cage in r9 cannot contain 5 - eliminate it

10 cage in r9 cannot be 3,7 or 1,9 - eliminate 1/3

12 cage in r8 cannot contain 6 - eliminate it

10 cage in r8 cannot contain 5, else it would be 2,3,5, invalidating the 12 cage in r8.

10 cage in r8 must contain a 1 - eliminate 1 from other cells in r8

7,28,10,12,12,10 cages in r8/9 sum to 79, leaving 11. The possibilities for 11 are 2&9, 5&6 - eliminate 3/7

11,21 cages in r9 sum to 32, leaving 13 in four cells. Eliminate 8/9 from these four cells

Can eliminate 2 from r9c8 due to the 10 cage, and 3 from r8c8 due to the 12 cage

Going back to that 13 in four cells, no way of making it if there's a 4 in r6 or r7, so eliminate

Similarly, can remove 3 from r8c9, and 6 from r9c9

Then remove 9 from r8c8, 4 from r9c8, due to the 12 and 10

Naked pair 5/7 in r8 and box 9

10 cage in r8 must now be 1,3,6 - eliminate 2 from this cage, and 6 from other cells in the row

Naked pair 2/9 in box 7

Eliminate 5 from the 7 cage in r9

5 in r9 constrained to the 12 cage, so 12 cage cannot contain an 8

Hidden single 8 in r9, and also fill in 2 in r9c9

Naked pair 1/3 in c9 and in 10 cage in c8/9

Naked singles 4,2 in that 10 cage

To make the bottom four cells of c9 sum to 13, r8c9 must be 7 - then r8c8 is 5.

Hidden single 9 in box 9

6 in box 9 constrained to c7 - eliminate 6 from rest of c7

11 cage in c9 must be 5,6 - eliminate other values

Naked pair 5/6 in c9 and box 3

If r9c5 or r9c6 is 3, cannot complete the 12 cage, so eliminate it from them

5 in r9 constrained to box 8 - eliminate other 5s from box 8

Hidden single 9 in box 8 - also fill in the 7 in r9c3

r7c4,r7c5,r7c6,r8c5,r8c6,r8c7,r9c5,r9c6,r9c7,r9c4 sum to 48 - this means r8c7 + r9c7 is 3 more than r8c4. As This sum cannot be 11, r8c4 cannot be 8.

Naked single 4 in r8c4, also fill in the 8 in r8c3

Now know that r8c7 + r9c7 is 7, and so r7c9 is 3 - also fill in the 1 in r6c9

Naked pair 1/6 in c7

Naked triple 1/5/6 in r7 and box 7

19 cage in c1 can only be 4,6,9 - fill in these digits

Naked singles 2,3 in box 7

Naked single 4 in r9c2

Cages 32+17+19+7+24 in c1/2/3 sum to 99 - this means r6c3 + r7c3 is 9 more than r1c2. Hence, r1c2 cannot be a 3

Can see that r6c2 + r6c3 must be 16 - fill in the 7 and 9

6 in r6 constrained to box 5 - eliminate other 6s from the box

One of r3c1,r4c1,r4c1 must be an 8. If not, we cannot fill the 17 cage - so eliminate 8 from other cells in c1


Looking at the 32 cage shows r2c2,r3c2 and r4c2 cannot be 5, or we cannot complete the cage - eliminate them

The ALS r3c1,r4c1,r5c1 excludes either 2 or 5 - this then leads to 3,6 as the only possibilities for r5c2

9 in r4 constrained to box 6 - eliminate other 9s

6 in c3 constrained to box 4 - eliminate other 6s

Naked single 3 in r5c2

Naked single 8 in r4c2

The ALS r3c1,r4c1,r5c1 now can't contain 2, to make the 17 cage consistent

Naked pair 1/5 in c2 and box 4

Naked pair 2/6 in c3

Naked single 8 in r3c1

Naked pair 4/9 in c9

Naked single 8 in c9

The 2 in the 15 cage can now only go in r1c4 - put it there

Naked single 7 in r1c1

Naked single 2 in r2c1

Hidden single 2 in box 3

31 cage in c7/8 contains a 2 and has no 8 - the only combination possible is 2,3,4,6,7,9 - eliminate 1s and 5s

Hidden single 5 in box 6

Naked triple 3/6/8 in box 5

Naked pair 1/5 in r4

Naked pair 2/4 in r4 and box 5

Naked singles 6,9 in r4

Naked single 4 in c9

Naked single 2 in r5

Naked pair 3/7 in box 6

Naked singles 4,6 in box 6

31 cage must have a 9 in r3c8

Naked single 6 in r3c2

Naked triple 1/3/5 in r3

Naked single 9 in r2c2

Naked single 7 in r3c6

34 cage and 11 cage in (ish) box 3 add to 45, meaning r1c5 + r1c6 is 15. The only posibility is 6/9, so eliminate all others

Naked pair 6/9 in r1 and box 2

Naked single 5 in r1c9

Naked single 1 in r1c2

Naked single 5 in r7c2

Naked single 1 in r7c3

Naked single 3 in r1c8

Naked single 4 in r1c3

Naked single 6 in r2c9

Naked single 7 in r4c8

Naked single 1 in r2c8

Naked single 3 in r4c7

The only combination for the 24 cage in r2 (ish) is 4,5,7,8 - eliminate 3 from cells

Naked triple 4/5/8 in r2

Naked singles in r2

Naked singles in boxes 1/3

Naked pair 1/3 in 21 cage

Naked single 5 in r4c4

Naked single 1 in r4c1

Naked single 5 in r5c1

Naked single 8 in r2c4

Naked single 7 in r7c4

Naked single 1 in r5c4

Naked single 3 in r3c4

Naked single 1 in r3c5

Naked single 9 in r5c6

Naked single 7 in r5c5

r6c6 must be 3 to finish the 24 cage

Naked single 6 in r6c4

Naked single 8 in r6c5

Naked single 2 in r7c5

Naked single 8 in r7c6

Naked single 4 in r4c5

Naked single 2 in r4c6

Naked single 5 in r2c5

Naked single 4 in r2c6

Naked single 6 in r9c5

Naked single 1 in r9c7

Naked single 5 in r9c6

Naked single 6 in r8c7

Naked single 1 in r8c6

Naked single 3 in r8c5

Naked single 9 in r1c5

Naked single 6 in r1c6

Done!

[999_Springs]

sclt:

listen. i have absolutely no idea how you managed to find me here. but seriously stop stalking my internet presence. it's creepy.

responded to solution path by facebook message, as you already know