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Solving Battleship: (Outside Sums)

This is a nice technique to use while solving Battleship puzzles. You may not always find it useful directly, but it comes in handy in parts when used correctly.

Take a look at Puzzle No.12

If you cannot start this puzzle without a guess, it has to be because you are not aware of this technique :-)

Take a look at the numbers outside the grid. The total of the right-side numbers is 20. The total of the bottom numbers is also 20. The total cells occupied by ships is 20 ( 1 x 4 + 2 x 3 + 3 x 2 + 4 x 1 ). Hence, even though the blank rows/columns can be any number, they have to be zero! The cells marked in red indicate it cannot be a ship.

Using the standard rules, you should easily be able to complete the puzzle.

This technique can be used effectively when the given sums are very low or very high. If the sum of numbers is 18, the blank row/column has to have just 2 cells with ships and so on...

Other Solving Techniques

Logic Masters India - January 2011 Sudoku Test

Logic Masters India announces the January 2011 Sudoku Test 'Prime Exotica'. It was held on 22nd-23rd January, 2011.
The author of the puzzles are Rakesh Rai.

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Download Instruction Booklet
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Password is Honorificabilitudinitatibus
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The list of sudokus that appeared in the test are:

1. DNA Sudoku
2. Kid Sudoku
3. Kombinance Sudoku
4. MultiTab Sudoku
5. Numerologidoku
6. Quad Sudoku
7. Peephole Sudoku
8. Poker Sudoku
9. Prime Number Sudoku
10. Rhombus Sudoku
11. Rossini Sudoku
12. Product Sudoku
13. Tennisdoku


1. Thomas Snyder (USA) - 660
2. David McNeill (UK) - 560
3. Hideaki Jo (Japan) - 545
4. don3232 (Taiwan) - 545
5. Michael Ley (Germany) - 517
6. WaterlooMathie (Canada) - 517
7. Rishi Puri (India) - 511
8. Nikola Zivanovic (Serbia) - 489
9. Frederique Rogeaux (France) - 481
10. Jason Zuffranieri (USA) - 479

Best Indians

7. Rishi Puri - 511
19. Rohan Rao - 397
34. Amit Sowani - 309
44. Jaipal Reddy - 266
47. Sumit Bothra - 260

Complete Results

Top quality puzzles. They were complete fun to solve and the concept usage was applied very effectively. Peephole Sudoku and Rossini Sudoku were my favourite from the set. In Peephole, for a few seconds I thought it had multiple solutions, but there was a nice little corner that made it unique. That was class! The 'anti-Rossini' solved very beautifully and logically.
I'm surprised to see so few people solve Numerologidoku. I thought after getting the sums, it solved very nicely.

Good start to the new year. Hoping to see more participants and more enjoyment in the tests to come!


I started my blog 30 months back. Yesterday, I got one of my best birthday gifts, of completing 50 followers of my blog :-)

Never did I expect so many people would follow my blog. I didn't even feel I would have 10 followers when I started! But something kept me going. Today, it feels great. It's an achievement that I am proud of.

Thank You all for your feedback, comments, participation, and anything related to this blog. I hope you find my blog useful and enjoyable (apart from some head-breaking puzzles!) and I hope to continue blogging and puzzling :-)

Domino Castle Variations Contest

A Domino Castle Variations Contest was held on 15th January, 2011 from 16:30 - 18:30 GMT (22:00 - 00:00 IST).

The goal is to build correct Domino Castles in each puzzle. Domino Castle is an interconnected figure formed by complete domino set (from 1-1 to 5-5 for small puzzles, from 1-1 to 7-7 for big puzzles and from 1-1 to 4-4 for examples). Each domino of the set is used exactly once. Domino halves which share an edge should have the same digit.

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Password is castldo2011


1. Nikola Zivanovic (Serbia) - 99
2. Shinichi Aoki (Japan) - 81
3. Takuya Sugimoto (Japan) - 69
4. Branko Ceranic (Serbia) - 63
5. Hideaki Jo (Japan) - 59
6. Jakub Hrazdira (Czech Republic) - 52
7. Masashi Sakata (Japan) - 51
8. Kota Morinishi (Japan) - 43
9. Stefano Forcolin (Italy) - 39
10. Rohan Rao (India) - 38

Best Indians

10. Rohan Rao - 38

Complete Results

Domino Castle is not one of my favourite puzzles, yet I gave it a shot, even though it being my birthday. I must admit, I enjoyed solving the set, though not very successfully :-)
I wonder why such wonderful contests have so few participants. Its just one of many question that every puzzler always seems to be having...

Logic Masters India - January 2011 Monthly Test

Logic Masters India announces the January Puzzle Test 'Puzzle Jackpot'. It is the first test of 2011 and it looks to be a great one!
The author of the puzzles are Serkan Yurekli (Turkey).

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Password is 306090domuzcukucgeni
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The list of puzzles that will appear in the test are:

1. Skyscraper
2. Gappy Skyscraper
3. Sum Skyscraper
4. Skyscraper Either/Or
5. Domino Skyscraper

6. Snake
7. Snake Egg
8. Dotted Snake
9. Japanese Snake
10. First Seen Snake

11. Kakuro
12. Gapped Kakuro
13. Magic Summer
14. Trid
15. Orbits

16. Tapa
17. Knapp Daneben Tapa
18. Tapa ?
19. Easy As Tapa
20. Tapa Filler

21. Crisscross
22. Missing Letters
23. Scrabble
24. Jumping Crossword
25. Crisscross Crash


1. Thomas Snyder (USA) - 1237.2
2. Ulrich Voigt (Germany) - 1237.2
3. Nikola Zivanovic (Serbia) - 1186.5
4. Hideaki Jo (Japan) - 1097.0
5. Florian Kirch (Germany) - 1022.2
6. Roland Voigt (Germany) - 997.2
7. Michael Ley (Germany) - 989.5
8. Branko Ceranic (Serbia) - 969.6
9. Psyho (Poland) - 963.5
10. Tomasz Strozak (Poland) - 934.8

Best Indians

35. Rohan Rao - 626.8
49. Jaipal Reddy - 503.0
50. Rakesh Rai - 499.5
51. Amit Sowani - 497.6
90. Harmeet Singh - 286

Complete Results

Very interesting concept. Points of puzzles were decided at the end of the test based on the number of people who solve each puzzle. More the people who solve a puzzle, lesser is the points. Wow!

Rules of 'Magic Summer'

Fill in the grid with digits 1 to 4 such that every row and column contains each number exactly once. Numbers outside the grid indicate the sums of all numbers appearing in the corresponding row (left to right) or column (top to bottom). These numbers are separated by at least one empty cell.



Solving Kakuro: (Minimax-Maximin)

Most easy Kakuro puzzles have this technique used.

Take a look at Puzzle No.211

Observe the last marked row. A sum of 10 with four cells has to be 1-2-3-4 using Unique Combinations. Hence the maximum value any of those four cells can take is 4.

Now observe the marked sum of 13. The sums can be 4-9, 5-8 or 6-7. Hence, the minimum number any of those two cells can take is 4.

The minimum value and the maximum value of the marked cell is 4. Hence, it has to be 4!

This technique can even be extended to non-overlapping range of values.

Other Solving Techniques

Solving Kakuro: (Unique Combinations)

This is the basic concept you need to use for solving a Kakuro. The list below gives the only possible combination of numbers for a given sum for different number of cells.

There are more such sets with higher area sizes, but these are the most commonly ones used.
The combination of numbers can occur in any order, but using these simple combinations can be very useful.

Other Solving Techniques

Solving Kakuro: (Overlapping Cells)

This technique can be used effectively once you learn how to use it correctly.

Take a look at Puzzle No.9

Using this technique, you can directly find out the number in the marked cell.

The sum of the five marked cells is 12 + 21 = 33 (Using the column sums).

But, the sum of the four marked cells is 11 + 16 = 27 (Using the row sums).

Simple subtraction, and you get 33 - 27 = 6 in the marked cell.

Use this technique and you are bound to improve your solving time!

Other Solving Techniques