## Golden Nugget Challenge

Post puzzles for others to solve here.

### Golden Nugget Challenge

.......39.....1..5..3.5.8....8.9...6.7...2...1..4.......9.8..5..2....6..4..7.....

The Easter Monster challenge was such fun I thought I'd try it on Golden nugget. The challenge is the same. Add a minimum number of Givens so that the resulting puzzle is solvable with at most one advanced move.

Leren
Leren

Posts: 3510
Joined: 03 June 2012

### Re: Golden Nugget Challenge

This is what I found. A single added given doesn't seem to be enough to make the sudoku easily solvable with a single advanced move.
Like the other puzzle, the puzzle has already one unique solution but complex techniques are required.

But there's something interesting going on, involving some of the 7s in the correct positions of that unique solution.
If you set as added given one or more of these 7s marked in red in this picture, they result in a wrong solved cell 9 (or in one case 4) which leads to an error.

The given is part of the correct solution, but because of a wrong apply of an exocet, the algorithm breaks the puzzle enterly.

I used Andrew Stuart's solver and Duncan's solver to test that.
Wecoc

Posts: 37
Joined: 08 April 2019
Location: Girona, Catalonia

### Re: Golden Nugget Challenge

Code: Select all
` *-----------* |...|...|.39| |...|..1|..5| |..3|.5.|8..| |---+---+---| |..8|.9.|..6| |.7.|..2|...| |1..|4..|...| |---+---+---| |3.9|68.|.5.| |.2.|...|6..| |4..|7..|...| *-----------*`

r7c1=3, r7c4=6
dan

ArkieTech

Posts: 3182
Joined: 29 May 2006
Location: NW Arkansas USA

### Re: Golden Nugget Challenge

My findings ordered by resulting difficulty (the last four being about the same or very subjective anyway):

1. (7,6)r1c1,r9c3 (-> singles)
2. (2,7)r1c7,r2c5 (-> pointing pair + singles)
3. (5,1)r8c15 (-> ALS XZ + singles)
4. (2,7)r17c7 (-> AIC + singles)
5. (6,2)r6c28 (-> Sue de Coq + singles)
6. (2,7)r2c3,r7c7 (-> AIC + singles)
Dan's (3,6)r7c14 (-> several basics + singles) would be third on this list. I actually picked my tactics from Dan's solution, i.e. shooting at trivalue cells from two directions. It means that there are many (most) two-cell combos I haven't tried (or won't), so lots of ground still uncovered -- not sure how fruitful, though, but would be interesting to know.
SpAce

Posts: 1309
Joined: 22 May 2017

### Re: Golden Nugget Challenge

My own results were :

7 r1c1 + 4 r2c7 : XYZ Wing + Basics
7 r1c1 + 6 r7c4 : Basics
7 r1c1 + 6 r9c3 : Singles

I also cottoned on to the "tactic" of placing extra Givens in positions that can see as many other Givens as possible, but in any event I just put 7 r1c1 and tried every other 2nd extra Given position.

When I got a Singles only result I left it at that. Leren
Leren

Posts: 3510
Joined: 03 June 2012

### Re: Golden Nugget Challenge

What's interesting is that pincering those trivalue cells worked pretty well here, but not with the Easter Monster.
SpAce

Posts: 1309
Joined: 22 May 2017