[R] Permutations

[Torsten Hothorn]

Hi, 

this is maybe not a real R problem but I want to solve this in R ;-)

Consider the set of all permutations of 1:N (=: S, say) and a fixed
element a from S. I now need to compute the number of permutations s from
S which are elementwise less or equal to a: | { s \in S | s <= a } |

Of cource, backtracking using a tree structure is possible. Does anyone
know an efficient way?

Torsten

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