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Find Nth in P(M,K) or C(M,K).


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#1 Benson

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Posted 27 September 2007 - 04:02 AM

1. If we have 9 colors of buttons and want to find all its permutations, we know that is P(9,9)=9!=362880. So, we can't remember all of them or find it quick. That's fine. But, how we find Nth in these 362880 permutations without record it first?

2. Same as 1, but if we want to find Nth from a permutation of M, K (M>=K and 1<= N <= P(M,K) ).

3. Same as 2. How about combination?

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#2 bonanova

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Posted 28 September 2007 - 06:38 AM

How do you determine an order? Without that, what does Nth mean?
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#3 Benson

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Posted 28 September 2007 - 07:37 AM

How do you determine an order? Without that, what does Nth mean?


Hint
1. The question is asking to find a "method" to generate a Nth sequence. It is not asking what the Nth sequence is.
2. Since there's no original sequence, the order is not important or impact the result.
3. It is a permutation. So, Sequence(N) needs to be unique in 362880 permutations.
And, Inside the sequence, every one color button needs to be listed 1 times.
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