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Difficult 7x7 Wednesday 24/7/19
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Posted on: Thu Jul 25, 2019 1:43 am

Posts: 79
Joined: Sun Jan 31, 2016 7:52 am
Difficult 7x7 Wednesday 24/7/19
I noticed that not many people solved the difficult 7x7 puzzle on 24/7, 45 had solved it when I last looked, I think this is not as many as usual.
I found it interesting so I thought I would share how I solved it.

1. e2 must be odd (parity)
2. c3 must be even (parity)
3. e1=4 (only cell in col. 4 with the value 4)
4. one of the cages d4,d5 or d7 must be 3,6, therefore none of those cages can be 6,3 (this would create a situation where there is more than 1 solution)
therefore d1=6
5. cg a1 =2&7
6. one of the cages d4,d5 or d7 must be 2,5 therefore e2=3
7. using parity rule in row 4 either a4 or a5 must be even (this seems of no benefit by itself, but it helps the next step)
8. columns 1&2 must have a total of 8 odd values,
with step 7 in mind we can count the odd values and we get 6 odd values and 1 cage (b2) that is unknown,
therefore cage b2 must have 2 odd values to give a total of 8 odd values in the first 2 columns
therefore cage b2 =5&7
9. there is a cross pair in cells a1,b1 & a2,b2 (value 7), remove 7 from all other cells in columns 1&2
10 from here it is all basic steps to solve the puzzle.

Posted on: Thu Jul 25, 2019 3:25 am

Posts: 229
Joined: Thu May 12, 2011 11:51 pm
Re: Difficult 7x7 Wednesday 24/7/19
I agree that this puzzle was an unusually difficult iteration of its ilk. On the other hand, it was a subscriber-only puzzle. I would wonder what the numbers of solvers are for other subscriber-only Wednesday 7x7 difficult puzzles.

Posted on: Thu Jul 25, 2019 12:37 pm

Posts: 47
Joined: Fri May 13, 2011 2:21 am
Re: Difficult 7x7 Wednesday 24/7/19
I usually don't mind this puzzle but I couldn't finish it, I worked out the parity ones but then just came up blank with the next step. Spent an hour or so trying to work for the opening but gave up in the end.

Posted on: Thu Jul 25, 2019 3:20 pm

Posts: 2687
Joined: Thu May 12, 2011 11:58 pm
Re: Difficult 7x7 Wednesday 24/7/19
For reference, here's the puzzle:

Posted on: Thu Jul 25, 2019 3:35 pm

Posts: 2687
Joined: Thu May 12, 2011 11:58 pm
Re: Difficult 7x7 Wednesday 24/7/19
sjs34 wrote:
I agree that this puzzle was an unusually difficult iteration of its ilk. On the other hand, it was a subscriber-only puzzle. I would wonder what the numbers of solvers are for other subscriber-only Wednesday 7x7 difficult puzzles.

If expressed again as a percentage of solved puzzles compared to the number of solved easy 4x4's that day,
it's number 3 on the all time list:

1. 2019-04-10: 5.05% (45)
2. 2014-03-12: 5.25% (45)
3. 2019-07-24: 5.37% (45)

So it's up there

Posted on: Thu Jul 25, 2019 11:14 pm

Posts: 728
Location: Ladysmith, BC, Canada
Joined: Fri May 13, 2011 1:37 am
Re: Difficult 7x7 Wednesday 24/7/19
A number of the puzzle was run off and then the different scenarios were tried until a couple of lucky guesses showed the most promise to continue with the puzzle to the last number......no magic numbers or great skill involved but a determination and a lot of time was required as did not want to lose out on the points:)

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