Saturday, 13 September 2014

nr. 940 - Daily League Sudoku - Even Group-Inequility Sudoku

I like the sudokus where you have to mark the odd-even cells. Such as Mathrax or yesterday Odd-Even Count Sudoku by Prasanna Seshadri.
Here is another this kind of sudoku.

Rules for Even Group-Inequility Sudoku:

Follow Sudoku rules. The given inequalities show that which side contain more even digits. Such as the first sign in the second row show that the first 3 cells contain more even digits then the second 3 cells.

Friday, 8 August 2014

nr. 941 - Daily League Sudoku - Sudoku Curve

This is my 100th post on this blog. Let's celebrate it with a sudoku. :P
Here is an easy practise puzzle for the upcoming WSC.

Rules for Sudoku Curve:
Follow Sudoku rules. The digits 1-9 appear once i each of the five 3x3 boxes and 10 bent "rows" (indicated by light curved lines). All "rows" contain exactly 9 cells.

Friday, 18 July 2014

nr. 942 - Daily League Sudoku - Rossini Sudoku

Today sudoku is an inequility variant which appeared on an LMI test in 2011 then I made two sudokus for  WSC2011.
This is my 3rd sudoku from this genre, and it is easier than my last Daily League Sudoku.
Have fun!

Rules for Rossini Sudoku

Standard Sudoku rules apply.
The arrows indicate that the nearest three digits in the row (column) are in ascending or descending order (increasing towards the direction the arrow is pointing towards). If there is no arrow outside a row/column, the nearest 3 digits therein cannot be in either ascending or descending order.

Friday, 4 July 2014

nr. 943 - Daily League Sudoku - Secret Code Sudoku

I'm not sure that anybody recognized it, but my last 2 sudokus were totally same.
First I made the Product Sudoku that I found a bit hard. So I change the clues into Quadruple, and I published it. But it was solved so quickly, so I tried the original version, too.
It's intresting that the product version is 8x harder.

Today sudoku is based on my Mastertrio puzzle which appeared on the WPC2011.
I can't determine its difficulty, but it's tend to be hard.
I hope you will enjoy it.

Rules for Secret Code Sudoku
Standard sudoku rules apply. Moreover find out the 4-digit secret code. Digit repeting is allowed in the code and the order of digits is not relevant. Some intersection contain a smallnumber. Each small number denotes the number of digits around it that are part of the code.
For instance if the code 1,3,3,4 and the number  3,4,4,7 has 2 matches: 3 and 4 are common.

Wednesday, 2 July 2014

How to solve Radar? II.

I show a possible solving line for nr. 944 - Radar puzzle.

First I mark the walls between 2-3 and 3-4 clues as I mentioned before. Then I mark the same clues next to edge. Don't forget C5-C6 next to the wall.

As always I start the solving eith the largest numbers. In R10 the clue in 9. There are 12 cells there, but because of the walls at least C4 or C5 is empty. and the C9-C10 pair is same.
So R10C2 and R10C11 cannot be empty.

Similarly R2C7 and R11C7 are part of a rectangle. Then we can use the same-edge trick. Moreover R10C7 is marked, too.

Then I check the small numbers. 2s and 3s have the advantage, that all cells are in in group in that row. 
We can mark many empty cells using these small numbers and the walls.
Such as R3C5 then R3C6 (same clues) and R3C9.
Then the top of C5 and C6.
R9C5 and R9C6 because of the 3 marked cells in the bottom of C7. The cloud in R1C7 continues to right.
R3C4 must be empty because of the same clues in R1-R2.
R12C4 is empty then R11C4, as well.
In C10, R3 is empty (C11 and C12 are same), then R1-R2. Moreover R9 is empty too, then R9C11-R9C12. Now the cloud in R10C11 continues to down 2 cells.

Now a trick in C10. The 3 cannot be in the top part. Because 7 in C11 cannot be 3+3+1.
And similarly R3C11 is empty. Now we can finish the whole bottom part.

Let's finish the puzzle. 6 in C8 cannot be 3+3 because of the 4 in C9. So R3C7-C8 are empty. And R4C7-C8-C9 are filled. This was the last relatively hard step.

Sunday, 22 June 2014

nr. 944 - Radar

This is the next part of my Radar tutorial.
The description of first trick, and the solution of example puzzle has already posted.

Now let's see the second trick, and a new practise puzzle.

If there are a 2 and 3 clue next to each other there is no rectangle that can part of both rows. 
Similarly if there are a 3 and 4 clue next to each other there is no rectangle that can part of both rows.

Because of every rectangle is at least 2 units wide. If a clue is 2 then there is only one 2-wide rectangle in that row. Similarly if a clue is 3 then there is only one rectangle in the corresponding row.
So a 2-wide and a 3-wide rectangle cannot be same.

Similarly a 4 clue can be a simple 4 or 2+2. It cannot part a 3-wide rectangle.

First I check if there is anywhere these kind of clues and I draw a bolded line between the two rows. It is a wall. These walls divide the grid into subregions.

In the next practise puzzle it is needed to use this trick and the previous one, too.
The biggest number is 9 in a 12x12 grid. There are 3 empty squares in that row, which seems too many.
But for instance there is a wall between R3 and R4.And it means that R3C7 or R4C7 is empty or both of them. These walls make it possible for the puzzlemaker to use a bit smaller numbers for starting.

Next time I will show the solving steps of this puzzle.

Friday, 20 June 2014

nr. 945 - Daily League Sudoku - Product Sudoku

My next puzzle in DLS series is much harder than the previous one.
This kind of sudoku is enjoyable for me, although the starting steps are quite boring. i.e. counting the prime factors of each clue.
Hence I added a pdf in which Ihave already did it.
If you like the math puzzle, but this one is too big for you, just visit my old site for easier Magic Squares with products.

Rules for Product Sudoku:
Follow classic sudoku rules. At some intersections of two crossing grid lines, a number is given. This number show the product of digits in the four adjacent cells.