How do you solve the circular table problem?
$begingroup$
One classic puzzle has many different forms, but the basic strategy is the same.
Once upon a time there was a crazy king who had a very wise minister
with him. The king had a habit of playing a strange game on a circular table.
The game was played as follows: The king told his minister a different number everyday -
let's say he says 5. Then minister would then arrange five people and ask
them to sit in a circular table with five chairs. Starting from a specific person, the king would then kill every
second person on the table, until only one remained at the end, to which he would give 1,000 gold coins.
For example, if there were five people on the table, starting from
person 1, he would kill person 2, person 4, person 1, and person 5 (skipping over persons 2 and 4 since they are already dead),
leaving person 3 as the survivor and winner.
Now the wise minister was so clever as to calculate the winner
beforehand as soon as king said the number, and asked his man to sit
at particular seat so as to not be killed and also win some gold.
How did the minister decide the winner?
mathematics josephus-problem
$endgroup$
add a comment |
$begingroup$
One classic puzzle has many different forms, but the basic strategy is the same.
Once upon a time there was a crazy king who had a very wise minister
with him. The king had a habit of playing a strange game on a circular table.
The game was played as follows: The king told his minister a different number everyday -
let's say he says 5. Then minister would then arrange five people and ask
them to sit in a circular table with five chairs. Starting from a specific person, the king would then kill every
second person on the table, until only one remained at the end, to which he would give 1,000 gold coins.
For example, if there were five people on the table, starting from
person 1, he would kill person 2, person 4, person 1, and person 5 (skipping over persons 2 and 4 since they are already dead),
leaving person 3 as the survivor and winner.
Now the wise minister was so clever as to calculate the winner
beforehand as soon as king said the number, and asked his man to sit
at particular seat so as to not be killed and also win some gold.
How did the minister decide the winner?
mathematics josephus-problem
$endgroup$
2
$begingroup$
How does the king decide where to start killing?
$endgroup$
– Kevin
May 22 '14 at 12:47
$begingroup$
Let's say chair very next to his place to sit is considered as first chair daily. But its the same everyday.
$endgroup$
– PM.
May 22 '14 at 13:16
add a comment |
$begingroup$
One classic puzzle has many different forms, but the basic strategy is the same.
Once upon a time there was a crazy king who had a very wise minister
with him. The king had a habit of playing a strange game on a circular table.
The game was played as follows: The king told his minister a different number everyday -
let's say he says 5. Then minister would then arrange five people and ask
them to sit in a circular table with five chairs. Starting from a specific person, the king would then kill every
second person on the table, until only one remained at the end, to which he would give 1,000 gold coins.
For example, if there were five people on the table, starting from
person 1, he would kill person 2, person 4, person 1, and person 5 (skipping over persons 2 and 4 since they are already dead),
leaving person 3 as the survivor and winner.
Now the wise minister was so clever as to calculate the winner
beforehand as soon as king said the number, and asked his man to sit
at particular seat so as to not be killed and also win some gold.
How did the minister decide the winner?
mathematics josephus-problem
$endgroup$
One classic puzzle has many different forms, but the basic strategy is the same.
Once upon a time there was a crazy king who had a very wise minister
with him. The king had a habit of playing a strange game on a circular table.
The game was played as follows: The king told his minister a different number everyday -
let's say he says 5. Then minister would then arrange five people and ask
them to sit in a circular table with five chairs. Starting from a specific person, the king would then kill every
second person on the table, until only one remained at the end, to which he would give 1,000 gold coins.
For example, if there were five people on the table, starting from
person 1, he would kill person 2, person 4, person 1, and person 5 (skipping over persons 2 and 4 since they are already dead),
leaving person 3 as the survivor and winner.
Now the wise minister was so clever as to calculate the winner
beforehand as soon as king said the number, and asked his man to sit
at particular seat so as to not be killed and also win some gold.
How did the minister decide the winner?
mathematics josephus-problem
mathematics josephus-problem
edited Jun 13 '14 at 21:16
Gilles
3,42731837
3,42731837
asked May 22 '14 at 11:25
PM.PM.
170313
170313
2
$begingroup$
How does the king decide where to start killing?
$endgroup$
– Kevin
May 22 '14 at 12:47
$begingroup$
Let's say chair very next to his place to sit is considered as first chair daily. But its the same everyday.
$endgroup$
– PM.
May 22 '14 at 13:16
add a comment |
2
$begingroup$
How does the king decide where to start killing?
$endgroup$
– Kevin
May 22 '14 at 12:47
$begingroup$
Let's say chair very next to his place to sit is considered as first chair daily. But its the same everyday.
$endgroup$
– PM.
May 22 '14 at 13:16
2
2
$begingroup$
How does the king decide where to start killing?
$endgroup$
– Kevin
May 22 '14 at 12:47
$begingroup$
How does the king decide where to start killing?
$endgroup$
– Kevin
May 22 '14 at 12:47
$begingroup$
Let's say chair very next to his place to sit is considered as first chair daily. But its the same everyday.
$endgroup$
– PM.
May 22 '14 at 13:16
$begingroup$
Let's say chair very next to his place to sit is considered as first chair daily. But its the same everyday.
$endgroup$
– PM.
May 22 '14 at 13:16
add a comment |
1 Answer
1
active
oldest
votes
$begingroup$
This is known as the Josephus problem. If the number of people $n$ is expressed as $n=2^m+p$, with $m$ as large as possible, the survivor is in seat $2p+1$ Another way to express it is to write $n$ in binary and rotate left one position. For example, let there be $19$ people at the table, so we write $19=2^4+3$ and the winner is $2cdot 3+1=7$, or $19_{10}=10011_2$ Left rotating one space gives $00111_2=7_{10}$
$endgroup$
$begingroup$
See also A006257.
$endgroup$
– SQB
May 22 '14 at 13:05
$begingroup$
Sorry for dumb question but I did not get the definition of m, n and p. Can you please explain what are the values of m,n and p in the example I explained in question?
$endgroup$
– PM.
May 22 '14 at 13:22
2
$begingroup$
In your example, $n=5, m=2, p=1$, because there are $5=2^2+1$ people at the table and the winner is in seat $2 cdot 1+1=3$. For another example (because with small numbers it can be confusing what comes from where), if there were $19$ people at the table, we would write $19=2^4+3$ and the winner would be in seat $2 cdot 3+1=7$
$endgroup$
– Ross Millikan
May 22 '14 at 13:29
add a comment |
Your Answer
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1 Answer
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oldest
votes
1 Answer
1
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oldest
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active
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votes
$begingroup$
This is known as the Josephus problem. If the number of people $n$ is expressed as $n=2^m+p$, with $m$ as large as possible, the survivor is in seat $2p+1$ Another way to express it is to write $n$ in binary and rotate left one position. For example, let there be $19$ people at the table, so we write $19=2^4+3$ and the winner is $2cdot 3+1=7$, or $19_{10}=10011_2$ Left rotating one space gives $00111_2=7_{10}$
$endgroup$
$begingroup$
See also A006257.
$endgroup$
– SQB
May 22 '14 at 13:05
$begingroup$
Sorry for dumb question but I did not get the definition of m, n and p. Can you please explain what are the values of m,n and p in the example I explained in question?
$endgroup$
– PM.
May 22 '14 at 13:22
2
$begingroup$
In your example, $n=5, m=2, p=1$, because there are $5=2^2+1$ people at the table and the winner is in seat $2 cdot 1+1=3$. For another example (because with small numbers it can be confusing what comes from where), if there were $19$ people at the table, we would write $19=2^4+3$ and the winner would be in seat $2 cdot 3+1=7$
$endgroup$
– Ross Millikan
May 22 '14 at 13:29
add a comment |
$begingroup$
This is known as the Josephus problem. If the number of people $n$ is expressed as $n=2^m+p$, with $m$ as large as possible, the survivor is in seat $2p+1$ Another way to express it is to write $n$ in binary and rotate left one position. For example, let there be $19$ people at the table, so we write $19=2^4+3$ and the winner is $2cdot 3+1=7$, or $19_{10}=10011_2$ Left rotating one space gives $00111_2=7_{10}$
$endgroup$
$begingroup$
See also A006257.
$endgroup$
– SQB
May 22 '14 at 13:05
$begingroup$
Sorry for dumb question but I did not get the definition of m, n and p. Can you please explain what are the values of m,n and p in the example I explained in question?
$endgroup$
– PM.
May 22 '14 at 13:22
2
$begingroup$
In your example, $n=5, m=2, p=1$, because there are $5=2^2+1$ people at the table and the winner is in seat $2 cdot 1+1=3$. For another example (because with small numbers it can be confusing what comes from where), if there were $19$ people at the table, we would write $19=2^4+3$ and the winner would be in seat $2 cdot 3+1=7$
$endgroup$
– Ross Millikan
May 22 '14 at 13:29
add a comment |
$begingroup$
This is known as the Josephus problem. If the number of people $n$ is expressed as $n=2^m+p$, with $m$ as large as possible, the survivor is in seat $2p+1$ Another way to express it is to write $n$ in binary and rotate left one position. For example, let there be $19$ people at the table, so we write $19=2^4+3$ and the winner is $2cdot 3+1=7$, or $19_{10}=10011_2$ Left rotating one space gives $00111_2=7_{10}$
$endgroup$
This is known as the Josephus problem. If the number of people $n$ is expressed as $n=2^m+p$, with $m$ as large as possible, the survivor is in seat $2p+1$ Another way to express it is to write $n$ in binary and rotate left one position. For example, let there be $19$ people at the table, so we write $19=2^4+3$ and the winner is $2cdot 3+1=7$, or $19_{10}=10011_2$ Left rotating one space gives $00111_2=7_{10}$
edited Jun 13 '14 at 20:08
Gilles
3,42731837
3,42731837
answered May 22 '14 at 13:04
Ross MillikanRoss Millikan
5,8732138
5,8732138
$begingroup$
See also A006257.
$endgroup$
– SQB
May 22 '14 at 13:05
$begingroup$
Sorry for dumb question but I did not get the definition of m, n and p. Can you please explain what are the values of m,n and p in the example I explained in question?
$endgroup$
– PM.
May 22 '14 at 13:22
2
$begingroup$
In your example, $n=5, m=2, p=1$, because there are $5=2^2+1$ people at the table and the winner is in seat $2 cdot 1+1=3$. For another example (because with small numbers it can be confusing what comes from where), if there were $19$ people at the table, we would write $19=2^4+3$ and the winner would be in seat $2 cdot 3+1=7$
$endgroup$
– Ross Millikan
May 22 '14 at 13:29
add a comment |
$begingroup$
See also A006257.
$endgroup$
– SQB
May 22 '14 at 13:05
$begingroup$
Sorry for dumb question but I did not get the definition of m, n and p. Can you please explain what are the values of m,n and p in the example I explained in question?
$endgroup$
– PM.
May 22 '14 at 13:22
2
$begingroup$
In your example, $n=5, m=2, p=1$, because there are $5=2^2+1$ people at the table and the winner is in seat $2 cdot 1+1=3$. For another example (because with small numbers it can be confusing what comes from where), if there were $19$ people at the table, we would write $19=2^4+3$ and the winner would be in seat $2 cdot 3+1=7$
$endgroup$
– Ross Millikan
May 22 '14 at 13:29
$begingroup$
See also A006257.
$endgroup$
– SQB
May 22 '14 at 13:05
$begingroup$
See also A006257.
$endgroup$
– SQB
May 22 '14 at 13:05
$begingroup$
Sorry for dumb question but I did not get the definition of m, n and p. Can you please explain what are the values of m,n and p in the example I explained in question?
$endgroup$
– PM.
May 22 '14 at 13:22
$begingroup$
Sorry for dumb question but I did not get the definition of m, n and p. Can you please explain what are the values of m,n and p in the example I explained in question?
$endgroup$
– PM.
May 22 '14 at 13:22
2
2
$begingroup$
In your example, $n=5, m=2, p=1$, because there are $5=2^2+1$ people at the table and the winner is in seat $2 cdot 1+1=3$. For another example (because with small numbers it can be confusing what comes from where), if there were $19$ people at the table, we would write $19=2^4+3$ and the winner would be in seat $2 cdot 3+1=7$
$endgroup$
– Ross Millikan
May 22 '14 at 13:29
$begingroup$
In your example, $n=5, m=2, p=1$, because there are $5=2^2+1$ people at the table and the winner is in seat $2 cdot 1+1=3$. For another example (because with small numbers it can be confusing what comes from where), if there were $19$ people at the table, we would write $19=2^4+3$ and the winner would be in seat $2 cdot 3+1=7$
$endgroup$
– Ross Millikan
May 22 '14 at 13:29
add a comment |
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2
$begingroup$
How does the king decide where to start killing?
$endgroup$
– Kevin
May 22 '14 at 12:47
$begingroup$
Let's say chair very next to his place to sit is considered as first chair daily. But its the same everyday.
$endgroup$
– PM.
May 22 '14 at 13:16