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13 The Joker | |

WSC and WPC 2017 -> WSC 2017 Instructions Booklet | 23 posts • Page 1 of 1 • 1 |

vopani |
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WSPC Organizer Posts: 739 Location: India | Round 13: The Joker Please post your questions about this round here. Corrections for v2: * In Sequence, R3C8 should be '4' and R6C8 should be '2'. This will be corrected. * In Clock-Faces, bottom-left corner is a black dot, not a white dot. This will be corrected. | ||

detuned |
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Posts: 152 Location: United Kingdom | 5. Sequences. Perhaps I've misunderstood something, but there are no solutions solving the set X49, with X between 1 and 9, such that the three numbers form an arithmetic progression. | ||

vopani |
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WSPC Organizer Posts: 739 Location: India | detuned - 2017-10-01 10:40 PM 5. Sequences. Perhaps I've misunderstood something, but there are no solutions solving the set X49, with X between 1 and 9, such that the three numbers form an arithmetic progression. You're right. Will get the example fixed. Thanks! | ||

detuned |
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Posts: 152 Location: United Kingdom | 8. Clock Faces The wording is loose here - so could you please confirm that the cell where the numbers start to increase from can be any of the cells in the 2x2 area? | ||

vopani |
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WSPC Organizer Posts: 739 Location: India | detuned - 2017-10-01 10:49 PM 8. Clock Faces The wording is loose here - so could you please confirm that the cell where the numbers start to increase from can be any of the cells in the 2x2 area? Yes, any. | ||

kishy72 |
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SM 2020 (Math) Author Posts: 417 Location: India | 5.Sequence Sudoku Cells in R2C6,R3C7 and R4C8 form a sequence.But the value of the joker should be -1 to satisfy that sequence which is not permissible.So how is that a sequence then and marked with a line? | ||

kishy72 |
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SM 2020 (Math) Author Posts: 417 Location: India | This query has been sorted previously.Sorry missed that. | ||

Hemant Kr Malani |
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Posts: 61 Location: India | 2. Pencil Marks sudoku The rule says that 'the joker may assume any of the given pencilmarks in the cell' but in r9c5 this is not true. 3. Non-Consecutive Same here. The rule says that 'the joker may assume any value that is not consecutive to the digit in its adjacent cell' but this is not true in many cells for example 4 is consecutive to both 3&5 in box 4. Can you please clarify which is correct--the rule or example?(I think the example) Edited by Hemant Kr Malani 2017-10-02 5:58 PM | ||

kishy72 |
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SM 2020 (Math) Author Posts: 417 Location: India | 9.Battenburg Sudoku Rules state all possible symbols are marked.Does the joker digit take its actual value when the vice versa rule comes into play or it could be any other digit ? For example, consider the following case with 5 as the joker digit : R1C1 = 1 ,R2C2 = 2, R2C1=4, R2C2 = 5 . Will this be marked by a Battenburg symbol or not necessarily marked ? | ||

Para |
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Posts: 315 Location: The Netherlands | kishy72 - 2017-10-02 5:58 PM 9.Battenburg Sudoku Rules state all possible symbols are marked.Does the joker digit take its actual value when the vice versa rule comes into play or it could be any other digit ? For example, consider the following case with 5 as the joker digit : R1C1 = 1 ,R2C2 = 2, R2C1=4, R2C2 = 5 . Will this be marked by a Battenburg symbol or not necessarily marked ? R8C23+R9C23 seems to confirm that it doesn't have to be marked. Just to reiterate on this. If the Joker has to be a 4 to fulfil a Battenburg marking in one 2x2 square and a 4 in that cell would also fulfil a Battenburg square in another place, that second square does not have to be marked as that Joker can just assume a random other digit for this other 2x2 square that wouldn't fulfil that Battenburg square? (This is just how this round in general works, right? A Joker can be as many different digits to fulfil all possible constraints or missing constraints set in the puzzle.) Edited by Para 2017-10-02 6:16 PM | ||

vopani |
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WSPC Organizer Posts: 739 Location: India | Hemant Kr Malani - 2017-10-02 5:57 PM 2. Pencil Marks sudoku The rule says that 'the joker may assume any of the given pencilmarks in the cell' but in r9c5 this is not true. 3. Non-Consecutive Same here. The rule says that 'the joker may assume any value that is not consecutive to the digit in its adjacent cell' but this is not true in many cells for example 4 is consecutive to both 3&5 in box 4. Can you please clarify which is correct--the rule or example?(I think the example) 2. In Pencilmarks, the digit '7' is the joker. R9C5 is a '7', the joker, and it can assume the value of '4' (or '5') to satisfy the pencilmark clue. 3. In Non Consecutive, the digit '4' is the joker. R5C2 is a '4', the joker, and it can assume the value of, say, '8' to satisfy non-consecutive constraint with the '3' to the left and it can assume the value of, say '2' (or even '8' again) to satisfy non-consecutive constraint with the '5' to the right. The rule and example are both correct as per these descriptions. | ||

vopani |
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WSPC Organizer Posts: 739 Location: India | Para - 2017-10-02 6:15 PM kishy72 - 2017-10-02 5:58 PM 9.Battenburg Sudoku Rules state all possible symbols are marked.Does the joker digit take its actual value when the vice versa rule comes into play or it could be any other digit ? For example, consider the following case with 5 as the joker digit : R1C1 = 1 ,R2C2 = 2, R2C1=4, R2C2 = 5 . Will this be marked by a Battenburg symbol or not necessarily marked ? R8C23+R9C23 seems to confirm that it doesn't have to be marked. Just to reiterate on this. If the Joker has to be a 4 to fulfil a Battenburg marking in one 2x2 square and a 4 in that cell would also fulfil a Battenburg square in another place, that second square does not have to be marked as that Joker can just assume a random other digit for this other 2x2 square that wouldn't fulfil that Battenburg square? (This is just how this round in general works, right? A Joker can be as many different digits to fulfil all possible constraints or missing constraints set in the puzzle.) This is correct. The joker can assume a value to satisfy a 2x2 region not having a Battenburg. @kishy72 Let me know if you still need help in understanding. | ||

Hemant Kr Malani |
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Posts: 61 Location: India | vopani - 2017-10-02 6:25 PM Hemant Kr Malani - 2017-10-02 5:57 PM 2. Pencil Marks sudoku The rule says that 'the joker may assume any of the given pencilmarks in the cell' but in r9c5 this is not true. 3. Non-Consecutive Same here. The rule says that 'the joker may assume any value that is not consecutive to the digit in its adjacent cell' but this is not true in many cells for example 4 is consecutive to both 3&5 in box 4. Can you please clarify which is correct--the rule or example?(I think the example) 2. In Pencilmarks, the digit '7' is the joker. R9C5 is a '7', the joker, and it can assume the value of '4' (or '5') to satisfy the pencilmark clue. 3. In Non Consecutive, the digit '4' is the joker. R5C2 is a '4', the joker, and it can assume the value of, say, '8' to satisfy non-consecutive constraint with the '3' to the left and it can assume the value of, say '2' (or even '8' again) to satisfy non-consecutive constraint with the '5' to the right. The rule and example are both correct as per these descriptions. Sorry I had some misunderstanding. Thanks for the clarification | ||

forcolin |
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Posts: 172 Location: ITALY | 8 Clock faces sudoku. I believe that the dot in the bottom left corner is of the wrong colour. In no way the joker can originate a clockwise sequence with the 2,4,6 placed in that way. Also, why there is not white dot in the intersection R89 C23? in this case the 5 could be replacing a 7. Or in the intersection R78 C23, in this case the 5 replaces a 9. This applies also for many other intersection where the joker is involved. In which sense the statement "All such dots are marked" should be interpreted? | ||

vopani |
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WSPC Organizer Posts: 739 Location: India | forcolin - 2017-10-03 4:25 AM 8 Clock faces sudoku. I believe that the dot in the bottom left corner is of the wrong colour. In no way the joker can originate a clockwise sequence with the 2,4,6 placed in that way. Yes, it should be a black dot. Will get this fixed. Thanks! Also, why there is not white dot in the intersection R89 C23? in this case the 5 could be replacing a 7. Or in the intersection R78 C23, in this case the 5 replaces a 9. This applies also for many other intersection where the joker is involved. In which sense the statement "All such dots are marked" should be interpreted? For R89C23 and other similar 2x2 areas with the joker, the '5' at R8C2 assumes a value, of, say, '4' for that 2x2 area, and hence there is no dot, because it can neither be white nor black. So, the joker digit forces the digits to not be clockwise or anticlockwise, just like in other areas where it can fit clockwise or anticlockwise. | ||

detuned |
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Posts: 152 Location: United Kingdom | Ok, so there might be two equally valid interpretations of the joker, the one which forcolin outlines and the one which Rohan has outlined. So it becomes a question of which interpretation takes precedence. Perhaps we need a statement along the lines of “there exists a value the joker can take so that the dot or lack of dot works” whilst making clear that is also possible to choose other values which break the rule. Rereading this entire round, it strikes me that this definition of what a joker is has not been adequately described to remove the ambiguities in the rules. Could I suggest this is added as a round note please? | ||

vopani |
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WSPC Organizer Posts: 739 Location: India | detuned - 2017-10-03 6:40 PM Ok, so there might be two equally valid interpretations of the joker, the one which forcolin outlines and the one which Rohan has outlined. So it becomes a question of which interpretation takes precedence. Perhaps we need a statement along the lines of “there exists a value the joker can take so that the dot or lack of dot works” whilst making clear that is also possible to choose other values which break the rule. Rereading this entire round, it strikes me that this definition of what a joker is has not been adequately described to remove the ambiguities in the rules. Could I suggest this is added as a round note please? We will review and get back on this. | ||

jzverina |
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Outside & Math (SM 16/17) Author Posts: 4 Location: Czech Republic | Hi, must be the joker always uniquely determinable? Example: in non-consecutive, if only numbers 4 and 5 break non-consecutivity (i.e. only consecutive pairs 45 appear in the grid), you can´t determine which of the digits is the joker. You need either 4 to touch 3 or 5 to touch 6 to uniquely identify the joker. | ||

vopani |
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WSPC Organizer Posts: 739 Location: India | jzverina - 2017-10-04 2:23 AM Hi, must be the joker always uniquely determinable? Example: in non-consecutive, if only numbers 4 and 5 break non-consecutivity (i.e. only consecutive pairs 45 appear in the grid), you can´t determine which of the digits is the joker. You need either 4 to touch 3 or 5 to touch 6 to uniquely identify the joker. In all puzzles, the joker digit will be uniquely determinable, just like the IB examples. So, the example you give will not happen. | ||

vopani |
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WSPC Organizer Posts: 739 Location: India | vopani - 2017-10-03 7:43 PM detuned - 2017-10-03 6:40 PM Ok, so there might be two equally valid interpretations of the joker, the one which forcolin outlines and the one which Rohan has outlined. So it becomes a question of which interpretation takes precedence. Perhaps we need a statement along the lines of “there exists a value the joker can take so that the dot or lack of dot works” whilst making clear that is also possible to choose other values which break the rule. Rereading this entire round, it strikes me that this definition of what a joker is has not been adequately described to remove the ambiguities in the rules. Could I suggest this is added as a round note please? We will review and get back on this. We have added clarification in Clock Faces and Battenburg "The joker may also assume a value such that it satisfies the constraint of a dot / battenburg not being marked." I hope that helps and makes it easier to understand. | ||

TiiT |
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Posts: 139 Location: Estonia | Maybe it's easyer to understand if you think that a Joker can break any rules. If there is no battenburg sign and you know there is Joker in that 2x2 area, then it doesn't matter what the other digits are. | ||

forcolin |
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Posts: 172 Location: ITALY | TiiT - 2017-10-07 12:58 PM Maybe it's easyer to understand if you think that a Joker can break any rules. If there is no battenburg sign and you know there is Joker in that 2x2 area, then it doesn't matter what the other digits are. this is not completely correct. At least half of the battenburg should be respected. In the example, it is obvious that the Battenburg is either 3 or 5 from the top corner. Hovever, R2C1 and R2C2 should still be one even number and one odd number, with the even number located below the joker. | ||

forcolin |
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Posts: 172 Location: ITALY | forcolin - 2017-10-08 10:17 PM ......, with the even number located below the joker. sorry, it's the other way round. the ODD number should be located under the joker | ||

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