Distributing cards among players












0












$begingroup$



Moderator Note: This is a current contest question on codechef.com.




N players sit around a round table. There are $n cdot m$ cards with unique numbers of range $1ldots ncdot m$.



Each player has $m$ cards. In each set of the game each player selects some card and everyone shows his card at the same time. Card of $i^{text{th}}$ player is compared to card of player $p[i]$. If it’s number is greater than the number on card of player $p[i]$, then $i^{text{th}}$ gets a point. $P$ is a permutation of sequence $0ldots n-1$.



But all players when playing want this game want to win. So, we decided to give cards in such way, that each player gets a point with probability larger than $frac{1}{2}$.



We need to tell all m cards of each of the n players playing the game.



Example : Let $n=3$ and $m=3$ and array $P$ be [2 0 1]. Then here answer is :



Player 0: 2 6 7
Player 1: 3 4 8
Player 2: 1 5 9


Here in this case each player has probability $frac{5}{9}$.
So i need to find the distribution of these cards.










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$endgroup$












  • $begingroup$
    I don't understand what $P$ is for. Since $P$ is known before the players select their cards, why not just agree that the players are rearranged so that $P[i] = i+1$?
    $endgroup$
    – MJD
    Jul 5 '14 at 20:44










  • $begingroup$
    @MJD Itjust shows that ith player card is compared with card of P[i]th player
    $endgroup$
    – user157452
    Jul 5 '14 at 20:45






  • 1




    $begingroup$
    @MJD: (a) it allow smaller cycle; (b) it's there to make the question more complicated. Since in a programming contest, anything that cause more difficulty is a chance for a program to fail, even if such difficulty is trivial mathematically.
    $endgroup$
    – Gina
    Jul 5 '14 at 20:54










  • $begingroup$
    @Gina Yeah right
    $endgroup$
    – user157452
    Jul 6 '14 at 4:50






  • 1




    $begingroup$
    This is a problem from an ongoing contest codechef.com/JULY14/problems/LUCKG . Kindly put this question on hold until the contest is over.
    $endgroup$
    – Mod
    Jul 6 '14 at 14:07
















0












$begingroup$



Moderator Note: This is a current contest question on codechef.com.




N players sit around a round table. There are $n cdot m$ cards with unique numbers of range $1ldots ncdot m$.



Each player has $m$ cards. In each set of the game each player selects some card and everyone shows his card at the same time. Card of $i^{text{th}}$ player is compared to card of player $p[i]$. If it’s number is greater than the number on card of player $p[i]$, then $i^{text{th}}$ gets a point. $P$ is a permutation of sequence $0ldots n-1$.



But all players when playing want this game want to win. So, we decided to give cards in such way, that each player gets a point with probability larger than $frac{1}{2}$.



We need to tell all m cards of each of the n players playing the game.



Example : Let $n=3$ and $m=3$ and array $P$ be [2 0 1]. Then here answer is :



Player 0: 2 6 7
Player 1: 3 4 8
Player 2: 1 5 9


Here in this case each player has probability $frac{5}{9}$.
So i need to find the distribution of these cards.










share|cite|improve this question











$endgroup$












  • $begingroup$
    I don't understand what $P$ is for. Since $P$ is known before the players select their cards, why not just agree that the players are rearranged so that $P[i] = i+1$?
    $endgroup$
    – MJD
    Jul 5 '14 at 20:44










  • $begingroup$
    @MJD Itjust shows that ith player card is compared with card of P[i]th player
    $endgroup$
    – user157452
    Jul 5 '14 at 20:45






  • 1




    $begingroup$
    @MJD: (a) it allow smaller cycle; (b) it's there to make the question more complicated. Since in a programming contest, anything that cause more difficulty is a chance for a program to fail, even if such difficulty is trivial mathematically.
    $endgroup$
    – Gina
    Jul 5 '14 at 20:54










  • $begingroup$
    @Gina Yeah right
    $endgroup$
    – user157452
    Jul 6 '14 at 4:50






  • 1




    $begingroup$
    This is a problem from an ongoing contest codechef.com/JULY14/problems/LUCKG . Kindly put this question on hold until the contest is over.
    $endgroup$
    – Mod
    Jul 6 '14 at 14:07














0












0








0





$begingroup$



Moderator Note: This is a current contest question on codechef.com.




N players sit around a round table. There are $n cdot m$ cards with unique numbers of range $1ldots ncdot m$.



Each player has $m$ cards. In each set of the game each player selects some card and everyone shows his card at the same time. Card of $i^{text{th}}$ player is compared to card of player $p[i]$. If it’s number is greater than the number on card of player $p[i]$, then $i^{text{th}}$ gets a point. $P$ is a permutation of sequence $0ldots n-1$.



But all players when playing want this game want to win. So, we decided to give cards in such way, that each player gets a point with probability larger than $frac{1}{2}$.



We need to tell all m cards of each of the n players playing the game.



Example : Let $n=3$ and $m=3$ and array $P$ be [2 0 1]. Then here answer is :



Player 0: 2 6 7
Player 1: 3 4 8
Player 2: 1 5 9


Here in this case each player has probability $frac{5}{9}$.
So i need to find the distribution of these cards.










share|cite|improve this question











$endgroup$





Moderator Note: This is a current contest question on codechef.com.




N players sit around a round table. There are $n cdot m$ cards with unique numbers of range $1ldots ncdot m$.



Each player has $m$ cards. In each set of the game each player selects some card and everyone shows his card at the same time. Card of $i^{text{th}}$ player is compared to card of player $p[i]$. If it’s number is greater than the number on card of player $p[i]$, then $i^{text{th}}$ gets a point. $P$ is a permutation of sequence $0ldots n-1$.



But all players when playing want this game want to win. So, we decided to give cards in such way, that each player gets a point with probability larger than $frac{1}{2}$.



We need to tell all m cards of each of the n players playing the game.



Example : Let $n=3$ and $m=3$ and array $P$ be [2 0 1]. Then here answer is :



Player 0: 2 6 7
Player 1: 3 4 8
Player 2: 1 5 9


Here in this case each player has probability $frac{5}{9}$.
So i need to find the distribution of these cards.







probability combinatorics contest-math






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share|cite|improve this question













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edited Jul 7 '14 at 7:26









robjohn

270k27312639




270k27312639










asked Jul 5 '14 at 20:32









user157452user157452

7110




7110












  • $begingroup$
    I don't understand what $P$ is for. Since $P$ is known before the players select their cards, why not just agree that the players are rearranged so that $P[i] = i+1$?
    $endgroup$
    – MJD
    Jul 5 '14 at 20:44










  • $begingroup$
    @MJD Itjust shows that ith player card is compared with card of P[i]th player
    $endgroup$
    – user157452
    Jul 5 '14 at 20:45






  • 1




    $begingroup$
    @MJD: (a) it allow smaller cycle; (b) it's there to make the question more complicated. Since in a programming contest, anything that cause more difficulty is a chance for a program to fail, even if such difficulty is trivial mathematically.
    $endgroup$
    – Gina
    Jul 5 '14 at 20:54










  • $begingroup$
    @Gina Yeah right
    $endgroup$
    – user157452
    Jul 6 '14 at 4:50






  • 1




    $begingroup$
    This is a problem from an ongoing contest codechef.com/JULY14/problems/LUCKG . Kindly put this question on hold until the contest is over.
    $endgroup$
    – Mod
    Jul 6 '14 at 14:07


















  • $begingroup$
    I don't understand what $P$ is for. Since $P$ is known before the players select their cards, why not just agree that the players are rearranged so that $P[i] = i+1$?
    $endgroup$
    – MJD
    Jul 5 '14 at 20:44










  • $begingroup$
    @MJD Itjust shows that ith player card is compared with card of P[i]th player
    $endgroup$
    – user157452
    Jul 5 '14 at 20:45






  • 1




    $begingroup$
    @MJD: (a) it allow smaller cycle; (b) it's there to make the question more complicated. Since in a programming contest, anything that cause more difficulty is a chance for a program to fail, even if such difficulty is trivial mathematically.
    $endgroup$
    – Gina
    Jul 5 '14 at 20:54










  • $begingroup$
    @Gina Yeah right
    $endgroup$
    – user157452
    Jul 6 '14 at 4:50






  • 1




    $begingroup$
    This is a problem from an ongoing contest codechef.com/JULY14/problems/LUCKG . Kindly put this question on hold until the contest is over.
    $endgroup$
    – Mod
    Jul 6 '14 at 14:07
















$begingroup$
I don't understand what $P$ is for. Since $P$ is known before the players select their cards, why not just agree that the players are rearranged so that $P[i] = i+1$?
$endgroup$
– MJD
Jul 5 '14 at 20:44




$begingroup$
I don't understand what $P$ is for. Since $P$ is known before the players select their cards, why not just agree that the players are rearranged so that $P[i] = i+1$?
$endgroup$
– MJD
Jul 5 '14 at 20:44












$begingroup$
@MJD Itjust shows that ith player card is compared with card of P[i]th player
$endgroup$
– user157452
Jul 5 '14 at 20:45




$begingroup$
@MJD Itjust shows that ith player card is compared with card of P[i]th player
$endgroup$
– user157452
Jul 5 '14 at 20:45




1




1




$begingroup$
@MJD: (a) it allow smaller cycle; (b) it's there to make the question more complicated. Since in a programming contest, anything that cause more difficulty is a chance for a program to fail, even if such difficulty is trivial mathematically.
$endgroup$
– Gina
Jul 5 '14 at 20:54




$begingroup$
@MJD: (a) it allow smaller cycle; (b) it's there to make the question more complicated. Since in a programming contest, anything that cause more difficulty is a chance for a program to fail, even if such difficulty is trivial mathematically.
$endgroup$
– Gina
Jul 5 '14 at 20:54












$begingroup$
@Gina Yeah right
$endgroup$
– user157452
Jul 6 '14 at 4:50




$begingroup$
@Gina Yeah right
$endgroup$
– user157452
Jul 6 '14 at 4:50




1




1




$begingroup$
This is a problem from an ongoing contest codechef.com/JULY14/problems/LUCKG . Kindly put this question on hold until the contest is over.
$endgroup$
– Mod
Jul 6 '14 at 14:07




$begingroup$
This is a problem from an ongoing contest codechef.com/JULY14/problems/LUCKG . Kindly put this question on hold until the contest is over.
$endgroup$
– Mod
Jul 6 '14 at 14:07










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    Now that the contest has ended you can see successful submissions at https://www.codechef.com/JULY14/problems/LUCKG, on the sidebar to the right.






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      Now that the contest has ended you can see successful submissions at https://www.codechef.com/JULY14/problems/LUCKG, on the sidebar to the right.






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        $begingroup$

        Now that the contest has ended you can see successful submissions at https://www.codechef.com/JULY14/problems/LUCKG, on the sidebar to the right.






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        $endgroup$



        Now that the contest has ended you can see successful submissions at https://www.codechef.com/JULY14/problems/LUCKG, on the sidebar to the right.







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        answered Jan 7 at 9:09









        user574848user574848

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