Puzzle No. 457 : Hamle

Another practice puzzle for the WPC. Hamle seems to be a common type in some places, but its still pretty new to me. I don’t think I’d solved one before seeing it on the WPC IB. So I tried my hand at it and saw what could be done. The resultant puzzle probably has one nice (slightly obvious) deduction. Other than that, I think its normal stuff.

Rules – 

Move each of the given black circles to one of the four directions so that each of them moves the distance marked upon it. In the final position, cells with circles do not share an edge (they may touch diagonally, though), and all empty cells are connected. During the move, circles may exit and re-enter the grid, as long as their movement remains straight. An additional empty grid will be provided for this puzzle.

Rated – Medium.




Week in Beijing Part 3 : WSC Play-offs, WPC R1-R3

WSC Preliminary aftermath

Since there were just 3 rounds on Day 2, the Play-offs could happen soon after, with a lunch break in between. As of this point, we still did not know the results and I was still wondering if I’d done enough in the last 3 rounds to reach the top 20. We were hoping Rohan would make the play-offs but he didn’t have a great last 3 rounds, his expected scores made that really improbable, with it being more likely he’d dip from 12th. As it turns out, that was exactly the case when we saw the results, and I had made no mistakes, to take me higher than I expected at any point after Day 1’s disappointment. I finished 15th, and Rohan finished 16th. Great for the team to have two in the top 20, but it would’ve been nicer with 3. Unfortunately Rishi had some health problems coming into Day 2, and really fell backwards in the rankings. He ended 28th. Jaipal stayed consistently around the late 50s, and finished 58th.

In the aftermath, there were some really funny scores given, as the checkers were probably in a hurry to get the play-off relevant results up quickly, and didn’t pay as much attention to the rest. A few notable scores displayed on the score page were, Fred Stalder getting 15 for a round where he’d actually scored 154, David Jones getting 34 (I think) where he’d actually scored 340+, and the best one of all, Helen Arnold getting 774 for a round where she’d scored 74, pushing her from 102nd to 50th or something, till the changes were made. There’s a tragic story of how she fought valiantly for the points before losing them, but thats for another day.

WSC Playoffs

The Semi-finals involved the top 10 sitting in a row of 10 tables, with the first ranked player after the preliminaries getting a time advantage over 2nd, and so on. As they went forward, the rows had lesser tables, and thus players would get eliminated until they had 3 quickest solvers. Tiit Vunk was a runaway leader after the Preliminaries and had a 5 minute advantage. Bastien Vial-Jaime was at 2nd place. They both got through the first table fine. The second table, I’m told, had a Killer Sudoku. Here, both of them reached a complete standstill. In the meantime, the rest of the field managed to solve the Killer and move on, meaning that the top 2 seeds were immediately knocked out.

Fast forward a little, and the Semi-final was finished first by Kota Morinishi, ensuring him a place in the finals and a chance to choose 3 out of the 5 Sudokus that would be used for the 1-on-1 final. Jin Ce was the 2nd one to finish the semi-finals, followed by an injured Jakub Ondroušek (he had hurt his foot before even arriving for the WSC, and was in some protective gear and crutches) to complete the podium.

There would now be the finals between Kota and Jin. I have a bit of a hazy memory of all things until it was 2-2. For the last Sudoku, Kota had chosen a Medium (?) Classic. I don’t know what was left in the pool, but it seemed to be playing to Jin’s strengths (not that Kota is any slouch in Classics). It was quite a dramatic finish, with Kota finishing mere seconds after Jin, and then both having to wait for confirmation that they had solved correctly. Turns out both had, and Jin Ce was crowned the new World Champion.

WSC Aftermath

Right after this, I assembled the folks of the Daily League on facebook, and we had a group photo, with almost all the authors in order from Monday to Sunday (Stefan was out of place, he should be Thursday with Rishi). See for yourself. We have, from left to right, Monday (Tiit Vunk, Christoph Seeliger, Jakub Hrazdira, Fred Stalder), Out-of-Place-Thursday (Stefan Heine), Tuesday (me), Wednesday (Bastien Vial-Jaime), Thursday (Rishi Puri, Sinchai Rungsangrattanakul), Friday (Tom Collyer), Saturday (Bram de Laat), Sunday (Seungjae Kwak).








Then, we had the traditional underground puzzle racing start up, with the Japanese team taking part. We had Jason, the undisputed Kakuro Champion, and a bunch of Nikoli legends disputing that, with Byron on commentary and quite an audience. At one point I believe this had more audience than the Champion’s press conference. Obviously, the underground racing is a big deal 😛

I skipped the Mahjong game session for reasons I have now forgotten. Oh right, I think I was late, it had already started, so I went exploring… Moving on then, to the WPC doubt solving session. This was nice as the 4 author teams of the Around the World in 80 Puzzles rounds were called up to manage their own rounds. So it was Bram for Dutch Delight, me for Indian Intrigue, Thomas for Doubled Decathlon and Cedomir for Serbian Snacks, each answering questions about our respective rounds. The teams other than the author teams were given a table where they were to mark the round each teammate would skip. The question of the night came from Ulrich Voigt, asking if he could skip the Digital Round if he solved all 4 of these rounds! Anyway, onward to the next morning, the start of the WPC.

WPC Day 1

Round 1 : Welcome to China (Team Round) – 60 minutes

This round made use of rotating tables. Eight puzzles were close to the solver on the stationary part of the table, with each having 13 rows and 10 columns. Then there were eight grids of 7 rows and 10 columns on the rotating part, and solvers must match the two parts to solve 8 complete grids. The puzzles were in two groups of four: four region types, and four black/white circle types. This round was really fun and had a “Welcome” message with either the region or the circles making a letter in each grid.

I took the Double Back and the Masyu. The Masyu had a lot solved in the bottom itself. The Double Back was slower going and I had to wait for certain eliminations. But once I had the top, the Double Back solved smoothly and was an excellent puzzle. I had 2 possible top halves for the Masyu, so I then went to check on the others. Different Neighbours (Only 4 Digits) was done successfully, I think by Rohan, We also had the Corridors solved fine by Amit, and Star Battle finished, either by Rohan or Rajesh (I think Rajesh). Rajesh was finishing the Binaire, Rohan had moved to the LITS where Amit was stuck, and Amit had moved to the Yin Yang. So I first went over to check the LITS which Rohan had finished, and found an error. Thankfully he had a clear marking of the area from where he’d guessed, so we erased that much, and I was able to solve it while Rohan went over to help with the Yin Yang. I then went to check other grids, and reached the Binaire which Rajesh had finished by then. Again, I spotted an error. This error was only in the top half of 7 rows, and since it is a mainly row-constrained puzzle type, we took a shot and just erased the top and re-did it. It solved fine thankfully.

Now what was left were the Yin Yang and the Masyu. With time running out, we just made a guess on which was which, because both worked for Masyu, and no one on the team was strong enough at Yin Yang to spot the deduction that may have been needed. I quickly solved the Masyu with that top half. It may have been wrong, or we made a mistake in the Yin Yang. Either way, the Yin Yang just would not get solved, even with all four of us looking at it towards the end. Thankfully we get points for correctly solved grids even if the piece might have belonged to another puzzle for the ideal overall solution.

Score – 1750/2000.

Round 2 – Classic Puzzles (Individual Round) – 90 minutes.

This was a round filled with common puzzle types. Everything seemed normal except for the existence of a Sudoku +/-4 (which is the reason for my practice-turned-league-post yesterday). No complaints from here though. It is a nice variant, I like math variants, and I was looking forward to getting to it. Unfortunately, I never got to it except for the last 3 minutes, when I decided it’d be less of a risk to go back and try to fix the Radar puzzle I’d broken along the way. I succeeded in that, so I feel it was a smart choice. The highlight of this round, at least for me, was the Yajilin. It had all 0 clues, and had a constraint that forced in a whole lot of black cells. I didn’t see this constraint during competition but figured intuitively that that was the way to go. I got out 13 of the 16 puzzles in this round. Even though the 3 I missed (2 Domino Halves and the Sudoku) I felt pretty good about it. Score – 440/600.

Round 3 – Digital Puzzles (Individual Round) – 40 minutes.

Bad. Good puzzles, the ones I solved at least, but this went really bad for me. I got 4 puzzles done out of 9, and missed out on the Digital Price Tags, a high pointer, after coming really close. I later heard that the other big pointers were probably overvalued, but I haven’t checked them yet, so I can’t comment on that. Score – 140/400.

The next one will cover the rest of the WPC, including my own round, Indian Intrigue, and also why my finger seems to be more famous than my WPC performance right now.

Puzzle No. 456 : Sudoku +/-4 [Daily League]

More of the practice puzzles I wrote for Team India. This variation was in the WPC and IS pretty puzzly, but I’m pressed for time and this solved the purpose of a Sudoku post.

Remember that you can solve the puzzles from the League online on the Sudokucup Guest League page with a 24h delay. However, I spoke to Karel and chances are this one might not be interface friendly. Do check in tomorrow if you want to though, just in case.

Rules – 

Enter whole numbers between -4 and +4, inclusive, into the grid so that each row, column and region contains all possible numbers exactly once. Clues outside the grid indicate the sum of all numbers that appear between the clue and the cell containing zero in that row/column. Some cells already contain a number. However, the signs for these clues are not indicated, it is part of the puzzle to determine whether they are positive or negative values.

Rated – Hard.




Week in Beijing Part 2 : WSC Team, WPF GP Finals, WSC Day 2.

In my previous post, I had left it at the 5th round, which was the last individual round of day 1. However, there was still quite a bit left in Day 1, 3 Team rounds.

Round 6 : Ball Sudoku (25 minutes)

This round consisted of 6 9×9 grids and 12 4×4 grids. The 4×4 grids were already completely solved. Each of these 4x4s connected 2 2×2 corners of 9x9s. It was part of solving to determine which pieces connect where. At the end of all the connection, it would be possible to curve the connected structure into a ball. Oh and, of course, the 6 Sudokus had to be solved too. Each Sudoku solved gave 120 points.

This was another really bad round, in my opinion. There were 2 reasons for this. Firstly, there was absolutely no way this round was even remotely finishable in the allotted time. Only one team (Poland) managed to correctly solve up to 4 out of the 6 Sudokus. No other team even had 3. There were many 0 scores, and unfortunately, team India was one of them. My personal experience was that I almost had a Sudoku solved logically, but couldn’t get it done in time. The rest of the team reportedly guessed their way through to a solution in one, but I guess that turned out to be wrong later.

My second problem with this round was, if at all any team HAD finished, there would be 30 bonus points for, of all things, sticking the grids together. Fortunately (?) the fact that this round was too hard made certain that no one had to get to the ball part. Score – 0/750.

Round 7 : Match (30 minutes)

This was a far simpler(nicer) team round, that involved being given 8 variants, and matching them into 4 pairs of double variants to solve. The variants given were Diagonal, Killer, Windoku, Consecutive, Little Killer, Inequality, Odd-Even, Anti Knight. After team discussions it had come upon me to tackle the Little Killer and whatever we figured out as its pairing. It turned out to be Consecutive. The pair solved nicely. The one major negative for this round, however, was that both grids forming the match HAD to be filled. So after solving using markings from one grid in the other, you’re essentially required to copy everything into the pairing to gain points. This seems so pointless that the question on whether this is necessary was asked multiple times during the doubt solving sessions before the WSC.

So after copying my Little Killer solution into the Consecutive Grid, I saw that Anti-Knight/Killer pairing and Odd/Inequality pairing were getting close to a finish by Rohan, Jaipal and Rishi, but the Diagonal/Windoku pairing seemed impossible. So I quickly went to that and made a guess, got it wrong, made another guess, got it wrong again, so then was making my way through the sure path to solution, when time was up. We had all the rest though, and it seems the Diagonal/Windoku pair was too difficult for many teams. Score – 600/800.

Round 8 : Mahjong Sudoku (30 minutes)

The only difficulty with this round seemed to be to memorize all the Mahjong rules and the Mahjong suits, as this involved completing the grid using Mahjong tiles, following certain Mahjong grouping rules, and Classic Sudoku rules. In the end, our lack of familiarity with the suit differences probably cost  big here. We got the grouping part quickly enough, but then got stuck with using the classic rules because visualizing the suit eliminations just wasn’t happening. We guessed a little and were making progress, but had to remove all the tiles when time was nearing the end, because there were negative points. In the end, we’d placed 39 tiles, out of which one was wrong, which meant 10 negative points. 10 points each for the correct tiles. Score – 370/800.

This was the end of Day 1, and I think India was at 9th after these team rounds, which overall went really poorly.

WPF Grand Prix Finals. 

The Grand Prix was a series of 8 online contests held across the past year. The top 10 were to compete in a separate finals, which was held at this point of the week, right after WSC Day 1. I had placed 13th in the online contests, so though close, I didn’t make the finals. I did volunteer however, as a proctor in the finals. Basically, I was to check the solution of a solver, if wrong, give the sheet back, if correct, give the next sheet, as the 10 solvers raced through 8 Sudokus. “My solver” turned out to be the number 1 seed, Japan’s Kota Morinishi. It was a nice little challenge trying to read his handwriting (and I thought mine was messy!). He started off pretty slow, and was falling behind the rest even after starting with a time advantage as the 1 seed. However, he suddenly started blitzing through the 2nd half, and ended up winning. It was quite awesome watching him solve at that speed towards the end. The rest of the podium was completed by Tiit Vunk from Estonia and Jakub Ondroušek from the Czech Republic, at 2nd and 3rd respectively.

WSC Day 2

As we’d left it, Rohan was 12th, Rishi was 21st, and me 27th. I feel the need to mention that 😛 Day 2 went quite well for me.

Round 9 : Close Relatives (88 minutes)

The round was another variant round, but this time, there were pairs, with one being a common variant, and the other being a slight variation to that variant itself. In all, there were 16 Sudokus. I solved 12 of these, with many high pointers. The highest pointer, a 6-cell Outside Sudoku, is one of the 4 I didn’t solve. I stared at it for 5 minutes, and thought my time would be better spent elsewhere. I then went and promptly broke the Irregular Sudoku with the time coming to a close. Not a good end, but my score seemed solid nonetheless. Score – 422/600.

Round 10 : Great Wall (15 minutes)

Though I did this well enough I do have some criticism here. This was a round with 5 connected Classic Sudokus, forming a “wall” together. Each grid completed would fetch 20 points. The problem here was, the main solve path was restricted to be in a right-to-left direction. This, coupled with the low time of 15 minutes, meant that some solvers were “teased” by the left side, only to reach a dead end and need to rethink, whereas some solvers started from the right and had an easy solve. I was somewhere in between this as I started seeing left, but quickly switched to right, for some inexplicable, but lucky, reason. I ended up solving 4 of the 5 grids, and was really close to finishing the last grid too. Score – 80/100.

Round 11 : Lucky Number 8 (35 minutes)

This went well enough. Not really good, but just par, I think. I did 6 out of 8 of the variants which were all themed on the number 8, because of it being the 8th World Sudoku Championships. Unfortunately one of the ones I didn’t do was the highest pointer. Score – 154/230.

Oh and, we have a detailed article about the week in Beijing now, which doesn’t just deal with my personal experiences.

Week in Beijing Part 1 : WSC Day 1 (Round 1-5)

Its been a while since I returned home from China, but I’ve had to jump right in to a bunch of deadlines here and there. So today I’ll finally start recapping the events and then maybe posting some puzzles after that.

Most of team India, including myself, got late due to missing the connecting flight, and ended up missing the opening ceremony. So the first night was pretty meh. The next day, we first visited the Great Wall, and climbed wayyyyyy too many steps to reach the top-ish area. Meaning it was at the top of the wall, but there was an area further away which was even higher that we decided to miss. I’d like to think its because we didn’t have time, and not sheer exhaustion. I like to think a lot of things.

After that we went to the Bird’s Nest, and the Water Cube, to experience in general the venue of the Beijing Olympics. The highlight here was the part where first Jason Z and then me nonchalantly went and stood in front of the camera whose content appeared on the big screen in the Water Cube. It took a while for them to realize we hadn’t paid to stand there, and for us to realize its paid, and for them to explain to us whether we should pay or not. I still have no clue whether we should or not, so score 1 for foreign communications.

We came back mostly pretty exhausted from the Great Wall climb, which actually turned out to be a good thing because it adjusted our sleep cycles nicely, and we all slept at a pretty good time and woke up fresh for the competition the next day.

WSC Day 1

Round 1 : Easy Classics

This round featured 1 4×4, 3 6x6s and 14 9x9s with a duration of 30 minutes. I started from the last page here, finishing 7 9x9s, and then seeing I had just 7 minutes left, got the smaller sized ones done, and I still had a minute and a half, and I somehow managed to blitz through the easiest of the 9x9s just in time. Final score : 134/200.

Scores were updated at the end of this round. As I remember it, I think Rohan was 8th, Rishi was 21st and I was 23rd at this point. Obviously Classics isn’t my strength. The harder ones of this round struck a little bit of fear in some, including me, about the Hard Classics round coming up later, because the hardest here was 18 points and the easiest there was 22 points.

Round 2 : Common Variants

This round had 18 variants, some of which were in different dimensions like Star/Ring shapes, while the rest were your normal variations. This was an 88 minute round, which I felt pretty confident about. I didn’t have a great round though. I broke the Non-Consecutive, the Untouch and the Kropki. I re-did and fixed all of them, but obviously lost some time there. Was quite close to finishing a high point Inequality Sudoku towards the end, but couldn’t. In the end I’d solved 12 out of 18. Score : 419/600. This turned out to be quite good, and place me much better than the Classics round where I had no mistakes.

Round 3 : Jigsaw Sudoku

This round was not good. It was a 15 minute round, where we would be given a blank grid that was expanded in a way that you had 12 3×3 boxes still forming 3 boxes in each row and each column. Then, there were the envelopes, A, B and C. A was with minimal clues, and the Jigsaw could still be solved, B was with slightly more, and C was with even more. If a solver chose A, and solved it, they’d get 100 points, and be eligible for finishing bonus. 50 and 20 for B and C, with no bonus applicable.

The problem was that the grid, unlike the Instruction booklet grid, didn’t offer any easy limitations for placing pieces, which I think is necessary for a 15 minute round like this. I went about risking it with A though, and thought I had it, and was solving till the end when I spotted a mistake that could not be rectified. So with about 3 minutes left, I opened B, didn’t get much, then with 1 and a half minutes left I opened C. C had all the digits given and it was just about arranging the pieces correctly. I did this, but then had just 30 seconds to copy it all into the grid. Not enough.

Final score – 0/100. I spoke to Rishi and Tiit later, who both had a bonus in the round and both said they got lucky. There were many 0 scores here including the top solvers. I don’t see how a solver aspiring to be in the top 10 could’ve done anything other than choosing to go along with A. There should either have been more time to the round, or the grid should probably have given more than it did.

Rankings displayed after this round showed I’d actually climbed 2 rankings in spite of the 0 score, mainly because of my good score in round 2 and because 0 was a common score for the 3rd round.

Round 4 : Hard Classics

My initial worries after Round 1 proved unnecessary. In fact, this round was probably more finishable. The classics were hard, but just with a bunch of nice techniques thrown in. There were 8 classics, in a 35 minute round. I did 6 of them, but left 2 of the highest pointers. Not too much difference in points though. I ended up with 148/230 having lost partial points to my only “uncaught” mistake of the WSC, leaving 2 cells blank on a Classic.

Round 5 : Math Variants

This round was my biggest disappointment of the entire WSC. Its no 0 score like the 3rd round, but its a round where I did horribly. There were 8 Math based variants for 40 minutes. Math variants are usually my strength so I was looking at scoring well here. I started off well enough, solving 4 of them in under 20 minutes. What followed was absolute disaster as I kept breaking each of the 4 variants ending up with just the solved 4 for the round. Final score – 103/250. Meh.

At the end of this, I was 27th, Rohan was 12th and Rishi was 21st.

Tomorrow, I’ll cover Team Rounds, the GP Finals, and Day 2, which had just 3 individual rounds.

Puzzle No. 453 : Regional Snake

I’m still a little busy, and its looking like that will continue through November. So, I’m just gonna post the puzzles I wrote for team practice before WPC, one by one. I will post write-ups too, somewhere in between all that. As of now, I’m mainly devoting about 5 minutes a day of my schedule to the write-ups, so I’ll fill them in little by little 😛

I decided to post the Regional Snake today. It has, quite literally (!) a narrow solve path. But I still think it uses the regions nicely.

Rules – (copied from the WPC Instruction Booklet, Serbian Round (R7)) Find a snake in the grid whose body consists of horizontal and vertical segments and its total length is 45 cells. The snake’s body never touches itself, not even diagonally. The head and tail of the snake are not given. Numbers in each of the regions surrounded by thick lines denote the number of cells occupied by the snake in that region.

Rated – Hard.




Puzzle No. 452 : Tennis Sudoku [Daily League]

Hello all. I’m back in India, about 2-3 days ago, but I’m a bit delayed with posting puzzles or any write-ups about my time in Beijing simply because I’ve had to rush right into 2 deadlines here. Hopefully I’ll be able to post something substantial in the next few days.

The following is a Tennis Sudoku. Nothing fancy about it, just a nice little solve, maybe.

Remember that you can solve the puzzles from the League online on the Sudokucup Guest League page with a 24h delay.

Rules for Sudoku. Additionally, Adjacent cells containing valid scores for a set of tennis are marked with a ball. Adjacent cells with no marking must not contain valid scores. The list of valid scores is: 6-1, 6-2, 6-3, 6-4, 7-5, 7-6, 8-6, 9-7.

Rated – Easy-side Medium.




Puzzle No. 451 : Inside Skyscrapers Sudoku [Daily League]

This post has been scheduled to appear on Tuesday evening. If it appears before/after that, blame WordPress 😛 Anyway, this is a Sudoku I had written for Team India’s practice, and since as of today the relevant round will have been done in the morning, it can be shared to the general public. The Sudoku is quite challenging. I like how it turned out.

Remember that you can solve the puzzles from the League online on the Sudokucup Guest League page with a 24h delay.

Rules for Sudoku. Consider each number to be the height of a building. Digits within cells with arrows indicate how many buildings can be seen when looking in that direction from the focal cells (taller buildings conceal buildings smaller or of equal height behind them).

Rated – Hard.




Non-Puzzle Post : Update

Unfortunately, I am not able to keep to my schedule this week, as we are leaving for China tonight to participate in the World Sudoku and Puzzle Championships, and as always, I’m busy with packing and what not at the last minute. I am carrying my laptop though, so I’ll mostly be able to post stuff in the coming week, be it updates or puzzles.

I do actually have a good number of puzzles I’ve written for team India’s practice, and I’ll release them sometime after the WPC, so there’ll definitely be compensation for any inactivity during this week. I will post a Tuesday Sudoku for the league (provided of course my laptop doesn’t cause problems and the internet there’s fine), but beyond that I’m not sure, at least till 20th.

EDIT : See comments. Unfortunately, more than the Tuesday Sudoku isn’t possible till 20th.