Link to original post : nr. 948 - Daily League Sudoku - Quadruple Sudoku

This is a familiar sudoku variant. I think it is one of the easiest where there is no given numbers.


If you want to solve this sudoku online you can do it tomorrow at SudokuCup.

Rules for Quadruple Sudoku:
Follow classic sudoku rules. At some intersections of two crossing grid lines, a set of four numbers is given. These numbers must be placed in the four adjacent cells.




Posted in Daily League Sudoku, Sudoku

Link to original post : nr. 947 - Radar

Radar is one of my favourite puzzles. It's a well-known genre, but it's not especially popular recently.  Hence I will publish some puzzles, and I will share some solving tips.

I was thinking when I can say that this is a trick of the puzzle types.
I think  anything that more then a simple deduction is trick or pattern.

Such as in a Yin and Yang puzzle when in a 2x2 area there are 3 white circles then the 4th is black is just a simple deduction. But the edge connection is a trick.
Of course it is consequence of rules, so it is a logical deduction, but not a simple deduction.
My first 4 Yin and Yang puzzle on the Beginner Contest were solvable without any trick, but it is more faster if you use the tricks in trivial puzzle too.


Today I publish the 0th puzzle of the series. I call it 0th puzzle because it is solvable with simple deductions.

For example if there are N empty cells in a row, and it is required to fill N-1, then it is a simple deduction that the 2nd cell from the side cannot be empty.
Or if the clue is 3, then there is only one cloud in that row which is 3 cells width.


Normally I like creating 10x10 puzzles without given cloud parts. But when I make a trickless one, it is better to give some elements and to use a bigger size.

Rules for Radar







Posted in Daily League Sudoku, Sudoku

Link to original post : nr. 946 - Radar

This is the first part of the (mini) series that will show the tricks of Radar puzzle type.
Let's see the first trick.

If the first and second clue is same on any side, than the first and second row is totally same.
The same is true, if there is 0 among the clues. And its neighbour and its second neighbour is same.

This is a simple consequence of the rule that every rectangles is at least 2 cells width.
So if there is a shaded cell in first row it will continue in the second. And the two clues are same, so there is no more shaded cells in the second row.

Here is an example which use only this trick.
For instance if R3C1 is shaded then it is trivial that R3C2 is shaded too.
Because of the trick the inverse is also true.
If R3C2 is shaded then R3C1 is shaded too. 
This is not trivial, but it is not a too difficult consequnce.

Another example is that if R3C2 is empty then it is trivial that R3C1 is empty too.
But the inverse is also true.
If R3C1 is empty then R3C2 is empty too.

First I check both sides of the clue and mark this pattern to not forget to use this trick.
In this puzzle there are 4 places where 1st and 2nd clue are same. But R6 and R7 won't give any extra informations because of the zeros.
Next time I will show the first steps of this puzzle. 








Posted in Radar, Tutorial

Link to original post : 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.





Posted in Daily League Sudoku, Sudoku

Link to original post : 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.







Posted in Radar, Tutorial

Link to original post : 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.



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.





Posted in Radar, Tutorial

Link to original post : 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.






Posted in Daily League Sudoku, Sudoku

Link to original post : 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.





Posted in Daily League Sudoku, Sudoku

Link to original post : 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.





Posted in Daily League Sudoku, Sudoku

Link to original post : 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.





Posted in Daily League Sudoku, Sudoku