Sunday, 7 July 2013

Daily League Sudoku #20: Max Difference Sudoku and Ace Sudoku

I've been a bit busier lately and didn't find the time to write out my blog posts. So I'm using this to post the two Sudokus I had posted in the Daily League page in the last 2 weeks. They were both new ideas as far as I'm aware of, but both used familiar ideas, just used in a way not done before. I think I more often go for new ideas because I don't think I can add more to common Sudoku genres as there are already so many available online.

The first puzzle iss Max Difference Sudoku. It is a variant where the maximum difference between 2 adjacent digits are marked for some rows and columns. I liked the interactions as both high and low digits can be used to force placements if you use the clues appropriately. This is actually the second puzzle as I had made a bad deduction during construction, which made the whole puzzle fall apart. I think this one actually worked out better than the way first one should have worked.

The second puzzle is an Ace Sudoku. It's a tricky variant where each 3x3 region obeys one of two rules that have been used in other puzzle, namely that either adjacent digits can't have a difference of 1 or that adjacent digits can't sum to 11. You have to deduce which of these two rules applies for each region. I always like these choice puzzles. The most common way this has been used is All Odd Or All Even Sudoku. The construction for this one took a while. I had the opening set up pretty quickly, but then spend ages trying to figure out if I could place the remaining digits in this pattern, so that it was unique. Many tries ended up without a solution as some 3x3 regions wouldn't obey either of the rules and a few ended up with multiple solution. But after a while I managed to find this puzzle. It has a few tricky steps in the middle, where you need to find the critical steps to make progress. I like how it turned out though and think it really nicely uses the rules of the genre. The name of the puzzle is derived from the Ace in Blackjack.

Rules for Sudoku

Max Difference Sudoku

In this Sudoku numbers on the outside indicate the maximum difference between two adjacent digits in that row or column. The indicated difference has to appear at least once in that row or column.

Ace Sudoku

In this Sudoku within every 3x3 region neighbouring digits either don't have a difference of 1 or don't have a sum of 11. One of these rules is true for each 3x3 region, but the other one doesn't necessary have to be false. Which of these rules is true can differ between different 3x3 regions. There are no restrictions between adjacent digits in different 3x3 regions.

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