Rajib_119's blog

By Rajib_119, 7 years ago, In English

How can I find the 1000th permutation of 50!. Using Backtrack i can easily find the 100th permutation of 5! or 5th permutation of 3! which is 3 1 2.

 
 
 
 
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7 years ago, # |
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Assume that you have to find the K-th permutation with N elements. With fixed first element you can rearrange the other elements in (N-1)! ways. Now you can easily find the first element in the K-th permutation. Then do the same with the second element, and then with the third and so on.

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7 years ago, # |
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http://ideone.com/yP5KuJ

for understanding refer to Factorial number system Wiki page Complexity (n lg(n)^2 )