Unrank

Interface

Unknown

This function computes the permutation of given rank and size, as generated by the <em> Permutation Class 2 </em> component, but <em> without </em> generating all the previous permutations. This function may be used with the Maths/Combinatorics/Permutations/Rank component in order to give a method of recognizing certain permutations only by their rank number.

Example:

#include <codecogs/maths/combinatorics/permutations/unrank.h>
#include <iostream>
int main()
{
  std::cout << "The permutation of 10 elements and rank 124 is:";
  std::cout << std::endl;
  std::vector<int> result = Maths::Combinatorics::Permutations::unrank(10, 124);
  for (int i = 0; i < result.size(); i++)
    std::cout << result[i] << "  ";
  std::cout << std::endl;
  return 0;
}

Output:

The permutation of 10 elements and rank 124 is:
1  2  3  9  4  5  10  6  8  7

References:

SUBSET, a C++ library of combinatorial routines, http://www.csit.fsu.edu/~burkardt/cpp_src/subset/subset.html

Returns

the permutation of size n and given rank, as generated by the <em> Permutation Class 2 </em> component

Authors

Lucian Bentea (August 2005)

Source Code

Source code is available when you agree to a GP Licence or buy a Commercial Licence.

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