Possible number of bombs in minesweeper game












4












$begingroup$


This question is about the minesweeper game, and I really don't know how to think about this.



Suppose that we are playing the game and we have already opened some number of cells. Then the closed cells which are adjacent to certain set of open cells form a group of cells, which I call clusters. Here are some examples of clusters (closed cells inside the black borders):



clusters



For each cluster $C$ we can consider the set $M(C)$ of possible number of mines it can contain. For example, on the image above, for the cluster adjacent to cells with numbers 2 and 3, this set is ${3, 4, 5}$.



Suppose that we have some cluster $C$ and $a,b$ are respectively the possible minimum and maximum number of mines it can contain, and moreover $bgeq a+2$. Is it true that for every integer $cin(a,b)$ it can contain exactly $c$ mines?










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  • 2




    $begingroup$
    Do a search for "minesweeper is NP-complete"; that might give some ideas for how to construct a counterexample. (just guessing here)
    $endgroup$
    – Greg Martin
    Jun 12 '17 at 8:41
















4












$begingroup$


This question is about the minesweeper game, and I really don't know how to think about this.



Suppose that we are playing the game and we have already opened some number of cells. Then the closed cells which are adjacent to certain set of open cells form a group of cells, which I call clusters. Here are some examples of clusters (closed cells inside the black borders):



clusters



For each cluster $C$ we can consider the set $M(C)$ of possible number of mines it can contain. For example, on the image above, for the cluster adjacent to cells with numbers 2 and 3, this set is ${3, 4, 5}$.



Suppose that we have some cluster $C$ and $a,b$ are respectively the possible minimum and maximum number of mines it can contain, and moreover $bgeq a+2$. Is it true that for every integer $cin(a,b)$ it can contain exactly $c$ mines?










share|cite|improve this question











$endgroup$








  • 2




    $begingroup$
    Do a search for "minesweeper is NP-complete"; that might give some ideas for how to construct a counterexample. (just guessing here)
    $endgroup$
    – Greg Martin
    Jun 12 '17 at 8:41














4












4








4


2



$begingroup$


This question is about the minesweeper game, and I really don't know how to think about this.



Suppose that we are playing the game and we have already opened some number of cells. Then the closed cells which are adjacent to certain set of open cells form a group of cells, which I call clusters. Here are some examples of clusters (closed cells inside the black borders):



clusters



For each cluster $C$ we can consider the set $M(C)$ of possible number of mines it can contain. For example, on the image above, for the cluster adjacent to cells with numbers 2 and 3, this set is ${3, 4, 5}$.



Suppose that we have some cluster $C$ and $a,b$ are respectively the possible minimum and maximum number of mines it can contain, and moreover $bgeq a+2$. Is it true that for every integer $cin(a,b)$ it can contain exactly $c$ mines?










share|cite|improve this question











$endgroup$




This question is about the minesweeper game, and I really don't know how to think about this.



Suppose that we are playing the game and we have already opened some number of cells. Then the closed cells which are adjacent to certain set of open cells form a group of cells, which I call clusters. Here are some examples of clusters (closed cells inside the black borders):



clusters



For each cluster $C$ we can consider the set $M(C)$ of possible number of mines it can contain. For example, on the image above, for the cluster adjacent to cells with numbers 2 and 3, this set is ${3, 4, 5}$.



Suppose that we have some cluster $C$ and $a,b$ are respectively the possible minimum and maximum number of mines it can contain, and moreover $bgeq a+2$. Is it true that for every integer $cin(a,b)$ it can contain exactly $c$ mines?







combinatorics






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edited Jun 12 '17 at 9:03









N. F. Taussig

45.3k103358




45.3k103358










asked Jun 12 '17 at 8:16









C_MC_M

41939




41939








  • 2




    $begingroup$
    Do a search for "minesweeper is NP-complete"; that might give some ideas for how to construct a counterexample. (just guessing here)
    $endgroup$
    – Greg Martin
    Jun 12 '17 at 8:41














  • 2




    $begingroup$
    Do a search for "minesweeper is NP-complete"; that might give some ideas for how to construct a counterexample. (just guessing here)
    $endgroup$
    – Greg Martin
    Jun 12 '17 at 8:41








2




2




$begingroup$
Do a search for "minesweeper is NP-complete"; that might give some ideas for how to construct a counterexample. (just guessing here)
$endgroup$
– Greg Martin
Jun 12 '17 at 8:41




$begingroup$
Do a search for "minesweeper is NP-complete"; that might give some ideas for how to construct a counterexample. (just guessing here)
$endgroup$
– Greg Martin
Jun 12 '17 at 8:41










1 Answer
1






active

oldest

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5












$begingroup$

By counterexample, consider the following cluster:



                                              enter image description here



Since it is impossible for only two of the three lowest flags to share a common mine, either a mine is placed in between the three flags, or one mine is placed for every flag. As such, this cluster can hold either $a = 13$ mines, or $b = 15 geq a+2$ mines.






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  • $begingroup$
    Beautiful example. Thank you!
    $endgroup$
    – C_M
    Jun 12 '17 at 10:10












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1 Answer
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1 Answer
1






active

oldest

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active

oldest

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active

oldest

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5












$begingroup$

By counterexample, consider the following cluster:



                                              enter image description here



Since it is impossible for only two of the three lowest flags to share a common mine, either a mine is placed in between the three flags, or one mine is placed for every flag. As such, this cluster can hold either $a = 13$ mines, or $b = 15 geq a+2$ mines.






share|cite|improve this answer











$endgroup$













  • $begingroup$
    Beautiful example. Thank you!
    $endgroup$
    – C_M
    Jun 12 '17 at 10:10
















5












$begingroup$

By counterexample, consider the following cluster:



                                              enter image description here



Since it is impossible for only two of the three lowest flags to share a common mine, either a mine is placed in between the three flags, or one mine is placed for every flag. As such, this cluster can hold either $a = 13$ mines, or $b = 15 geq a+2$ mines.






share|cite|improve this answer











$endgroup$













  • $begingroup$
    Beautiful example. Thank you!
    $endgroup$
    – C_M
    Jun 12 '17 at 10:10














5












5








5





$begingroup$

By counterexample, consider the following cluster:



                                              enter image description here



Since it is impossible for only two of the three lowest flags to share a common mine, either a mine is placed in between the three flags, or one mine is placed for every flag. As such, this cluster can hold either $a = 13$ mines, or $b = 15 geq a+2$ mines.






share|cite|improve this answer











$endgroup$



By counterexample, consider the following cluster:



                                              enter image description here



Since it is impossible for only two of the three lowest flags to share a common mine, either a mine is placed in between the three flags, or one mine is placed for every flag. As such, this cluster can hold either $a = 13$ mines, or $b = 15 geq a+2$ mines.







share|cite|improve this answer














share|cite|improve this answer



share|cite|improve this answer








edited Feb 2 at 20:41

























answered Jun 12 '17 at 9:30









jvdhooftjvdhooft

5,65961641




5,65961641












  • $begingroup$
    Beautiful example. Thank you!
    $endgroup$
    – C_M
    Jun 12 '17 at 10:10


















  • $begingroup$
    Beautiful example. Thank you!
    $endgroup$
    – C_M
    Jun 12 '17 at 10:10
















$begingroup$
Beautiful example. Thank you!
$endgroup$
– C_M
Jun 12 '17 at 10:10




$begingroup$
Beautiful example. Thank you!
$endgroup$
– C_M
Jun 12 '17 at 10:10


















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