Sudoku GP 2020

The new Sudoku GP season is about to begin. The first round starts the day after tomorrow - January 3rd. The instructions were published today and are available here: https://gp.worldpuzzle.org/content/instruction-booklet This time I will try to write more before and after the competitions and make summaries. Hopefully there will be many active participants. This is an opportunity to develop your Sudoku solving skills and compare them with the best in the world.

In the first round, the first 6 sudokus are definitely mandatory for the Vindi solvers - 5 classic and diagonal sudokus. If there is time left, I definitely recommend trying Quadruple sudoku and Product sudoku. Both are extremely simple variants and do not give very many points - so they should probably be more or less manageable for the average solver. 7. Quadruple - At the beginning, you have to look for common parts in two adjacent 2x2 areas. Sometimes they touch each other sideways and sometimes at the corners. In addition, it is also recommended to check whether sometimes there are individual squares in one 3x3 box where no clues are given. Sometimes it is also possible to write down the variants there (for example, in the example problem row7column7 there is a single box where you have to write 3, because in this 3x3 box the number 3 is not in any of the given clue numbers. 8. Product - here you simply need to know the 10x10 multiplication table. You need to know which variants there are to get the desired product. For example, for number 24 it is possible to get 3x8 and 4x6. It is recommended to write down the variants for each product. It gets more complicated from there. But if I have to recommend something, then number 12 Irregular and Alternating stripes sudoku could be one that is suitable for Vind users. 12 Irregular & Alternating stripes - NB! The numbers on the lines cannot be repeated and must alternate large-small-large-small. Since there are more than one large number, if possible, you should note which ones are large. I always circle the larger numbers if it is possible to tell where the large numbers are. Otherwise, sudoku rules. 9 Anti windoku - do not mess with windoku. There are 4 different numbers in the gray box. It is difficult to say what else is wise. 10 Big bands sudoku - I recommend that you circle the numbers that are repeated on the same strip on the bars given next to you. Maybe this will help you better place and exclude them. This is a task that it is even recommended to try to start somewhere at the end. Otherwise, you may just be left admiring it. 11 Battenburg Little killer - Be sure to mark the even and odd numbers that are known. One option is to circle the even number and make a dot on the odd number. And this even if, for example, the number is not known, but it is known whether it is even or odd. One of the tips for solving Battenburg sudoku is that if a chess square hint is not given, then a 2x2 chess square pattern must not be formed from even-odd numbers. And this must be used when solving. In general, however, it is not recommended to solve it first. This can be quite difficult. You need experience solving Battenburg and Little Killer. 13 Distance Sudoku - at first you need to look for larger distances. The maximum possible is 8. This means that these 2 numbers are in the first and last squares of the same row. If there is 7, then there are 2 options. If there is 6, then there are three options, but at least you are sure in which 3x3 box each number is located. Smaller distances are more complicated and they come into play in a later phase. Be sure to cross out the hint when the condition is met. This makes it easy to keep track of which hints have already been used and which ones still need to be followed in order to be able to solve the Sudoku. Good luck and have fun solving!

Thank you Tiit! For the first time, I understood all the tasks thanks to you. But in the end, it went as always, I did the mandatory ones and then I went to work on the task that gave the most points, but I didn't have time.

Many people have probably experienced this, that you go to solve an expensive task and then you don't get it done. I have experienced the same thing many times myself and have both failed and succeeded. Sometimes you have to take risks - especially when it's a task that is not completely unfamiliar. In the end, experience pays off and with each round, this experience increases. I'm glad my brief description was useful.

The results of the 1st round are available. https://gp.worldpuzzle.org/content/preliminary-results-wpf-gp-sudoku-1 I also made a table this time to keep track of the points between Estonians. That way, maybe you can get a good overview after each round. It seems like it will turn out. You can also make suggestions, for example, to supplement the table. Excel suffers from a lot in general.

The 2nd round guide is available. Some suggestions for solving may also be useful. I'll try to generate some ideas here that may be helpful. 1-6 classic and 7 diagonal are again those that should be very suitable for wind solvers. 8. Anti-diagonal The diagonal has 3 different numbers - the same 3 numbers must be repeated on one diagonal in all boxes. I recommend writing down in a corner somewhere what numbers can be on this diagonal. For example, the main diagonal of the example problem (from top left to bottom right) cannot have 2,4,5,6,9, because they already exist in the boxes where this diagonal passes and they are not on the diagonal. Consequently, the diagonal must have 3 pieces of the numbers 1,3,7 and 8. This sometimes helps to solve faster. 9. Windoku. in addition to the gray areas, this sudoku also has different areas where the numbers 1-9 must be. For example, rows 2, 3 and 4. There are two gray areas with numbers 1-9. Consequently, the numbers 1-9 must be in the remaining white squares. And if you mark out all possible areas in this way, then there will be 9 squares for the entire sudoku (in the corners, in the middle of the edges and in the center of the sudoku), where the numbers 1-9 must also be. You can check in the example problem that this is indeed the case. If you get stuck when solving, it is worth keeping an eye on these things. 10. Anti-Windoku. It is always worth noting that each gray area has 4 numbers. There are also 4 gray squares in the 3x3 boxes in the corners. This is helpful when solving if there is a number somewhere else in the gray square - then this number must always be in the gray area in the corner 3x3 box. 11. Arrow sudoku. One option is to solve large numbers digit by digit (for example 9). Since you can't write the number 9 on the arrow, it's often possible to place the number 9 early. Next, you need to look for longer arrows and mark out possible variants in different squares. If you don't have experience and math isn't your best friend, you don't have to solve this sudoku first. 12. Thermo sudoku I recommend marking out all the possibilities for longer thermometers that are possible to write on this thermometer. Often, two thermometers on the same line can be solved in some part this way. The task gives 80 points, which means that it is probably a fairly difficult task. 13. Tic-Tac-Toe The gray number in the middle box shows whether the corresponding 3x3 box has 3 even or odd numbers in a row. There cannot be 3 opposite numbers in a row. Accordingly, the following principles apply, which are worth knowing: If there is an even number in the gray square, then the numbers on the diagonal must form a triple in the corresponding 3x3 box. The middle number must also be even. See the answer to the example problem. If the even numbers were not on the diagonal, then a triple of odd numbers would definitely form in that box, and this would be contrary to the rules. The opposite principle does not apply, because there are 5 odd numbers and the even numbers do not necessarily have to be on the diagonal. 14. Hidden clone It is even difficult to recommend here, because I have never solved it myself. If I solve it and discover something, I can post it here. Apparently, you should just go and solve it if you find a place where it would fit. And if it does not fit, delete it and try somewhere else. There are probably very few possible clone locations, and sometimes experimenting can bring a quick result. You can also track the numbers that are in the gray box and that occur the most. And it should be noted that since the gray area is quite large, this already limits the possible locations of the clones. However, it is not known how large these clones are and how many there are. There may be all kinds of surprises here.

Round 2 has begun.

The results of the 2nd round are out, as well as the overall results after the 2nd round. https://gp.worldpuzzle.org/content/sudoku-gp I also made a summary table of the Estonians' results. It is clear that those who did not participate in the 2nd round lost their places a little. However, the rest have generally improved their places.

The 3rd round guide is available. I'll try to make a small summary here after I've gone through the tasks myself, so that I can solve them. The host country is Hungary.

The puzzle solvers are probably only used to classic sudoku this time, but I would definitely recommend trying the Extra region sudoku. It doesn't give many points and you just have to make sure that the gray areas also have the numbers 1-9. 7. Extra region. It's hard to give any good tips. Maybe you could keep track of 3x3 boxes and gray areas. Find a 3x3 box with the most gray squares. The white squares in this 3x3 box contain the same numbers as the gray squares outside this box (if they are part of the same shape). NB! The sample problem is difficult, the actual problem is definitely easier. 8. Battenburg. Mark out even-even numbers. I draw a circle around the even number and mark a dot for the odd number, for example. And also make sure that if the chessboard sign is not given, then a 2x2 chess square cannot be formed from even and odd numbers. It is often possible to do all of these markings and then solve the odd-even sudoku, which is very easy. The task gives few points and is probably relatively easy. Additional tip: If there is a chessboard mark somewhere and next to this mark there is an even and an odd number next to it, then it is also possible to mark all 4 numbers next to the chessboard clue. In this case, the given two (even and odd) and the numbers touching them must not form such a pattern (otherwise the clue would be marked there). This trick must be used often. Solve the example problem and if it works, you can feel free to try it. The example problem is very easy. 9. Clock sudoku It is important to remember that the first number can only be 1 or 2. If the first number is 2, then the second number can only be 1 and 3. Mark all the options. The third number can only be 1,2,3,4,5. The last number can be any. The example problem is very easy. If you can solve it quickly, then the competition problem should not cause any problems either. 10. Fortress. I recommend starting with No. 9. If you are not making progress, then with No. 1. You should also pay attention to the white squares that are surrounded by only white squares. You can still put No. 9 there. And in the same way, you can put 1 on a gray square if it is surrounded by gray squares. If you do not pay attention to this, then you often make a mistake when solving. If you start with No. 9 and you can more or less find 9, then continue with 8s, then 7s, etc. Sometimes this helps. You can also look for long gray lines, for example. There are sometimes very few options where to write No. 1s. And similarly, if there are many white squares next to this gray line, then there cannot be many options where to write No. 9. The example problem is quite easy. 11. Renban I recommend writing down the numbers that must definitely be in the gray area. For example, if there is an area of 5 squares, then there must always be the number 5. Then try to find some numbers that cannot be in this area. For example, if there is an area of 5 squares and the number 7 cannot definitely be there, then the numbers 1,2,3,4,5,6 are available, and since this area is 5 squares, the certain numbers are 2,3,4,5, and either 1 or 6. 12. Mini-max. At first, look for large and small numbers where there cannot be many variants. For example, if the number 15 is given, then the largest and smallest numbers must be 6 and 9. (7 and 8 cannot be, because then it is not possible to find the 3rd number between them). Similarly, if 5 is given, then only 1 and 4 can be there. It is also worth noting that if, for example, the numbers 8, 9 and 12 are given in the same box, then number 9 can only be in the row where 12 is. Similarly, if 7, 11 and 13 are given, then number 1 can only be where 7 is. In general, it is not recommended to solve this problem if you have not encountered it. It usually takes a lot of time. The example problem is quite decent, but nothing too bad. 13. Distance sudoku. If the distance is 8, then the numbers are in the first and last box. If the distance is 7, then there are 2 options. If the distance is 6, then the numbers are in the first and last box in the same position. It is worth starting with the larger ones and writing out the options so that you understand which direction they refer to. The example problem was very easy. The competition problem is probably difficult because it gives a lot of points. 14. Quad max sudoku Here, you should usually start solving with large numbers. For example, the number 9 cannot be in a place that is touched by an arrow but is not at the tip of the arrow. In general, you need to constantly monitor where you can put larger numbers. It may also be useful to think about which numbers can be in those squares that are not the largest. Sometimes it turns out that there must be quite large numbers there too. In this case, this will eliminate some of the options at the tip of the arrow. Since the task gives a lot of points, it is also very difficult. The example task is very easy. If you cannot handle it reasonably, then it is not worth attempting this task in the competition.