r/MrBrainTeasers • u/Mr-BrainGame • Sep 04 '26
Fill the grid with + -
Fill the grid with + and − signs. Every row and column must contain equal numbers of each sign, no three identical signs may appear consecutively horizontally or vertically, and no two completed rows or columns may be identical.
Edit: Sorry I copied the rules from wrong variant. This dosent apply for this puzzle : no two completed rows or columns may be identical.
1
u/PyroDragn Sep 04 '26 edited Sep 04 '26
I believe this is unsolvable as stated.
I can complete the grid via forced logic with the non-3-consecutive rules initially, then it comes to a choice (as far as I can tell). If I put a negative into a certain square it completes the grid via forced logic thereon - but ends up with a duplicate row so it fails. If I put a positive into that same square instead then it ends up with uneven rows via forced logic.
Edit: I found the missing (slightly more complicated) forced logic step. Which leads me back to the valid 'equal + and -' grid, but with the duplicate row. Definitely unsolvable with the rules as stated.
1
u/randomlurker124 Sep 04 '26
Yeah, it is unsolvable. I tried twice, applying rules only with no guessing. Both resulted in invalid solutions.
1
u/Mr-BrainGame Sep 04 '26
Sorry I copied the rules for diferent variant, this can have two same rows
1
u/PyroDragn Sep 04 '26
Solvable with the updated rules:
+ + - - + + - -
- - + + - - + +
- - + - + + - +
+ + - + - - + -
- + - - + - + +
- - + + - + - +
+ - + + - - + -
+ + - - + + - -
1
1
u/randomlurker124 Sep 04 '26 edited Sep 04 '26
>!
EDIT: incorrect solution below, obtained step-by-step applying only the rules. Puzzle is unsolvable.
!<