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/* Author: Mark Moll */

#ifndef OMPL_DATASTRUCTURES_PERMUTATION_
#define OMPL_DATASTRUCTURES_PERMUTATION_

#include <boost/random/mersenne_twister.hpp>
#include <boost/random/uniform_int.hpp>
#include <boost/random/variate_generator.hpp>

namespace ompl
{

    /// \brief A permutation of indices into an array
    ///
    /// This class tends to be faster than std::shuffle when permute is called
    /// several times, since the random number generator doesn't need to be
    /// allocated each time.
    class Permutation : public std::vector<int>
    {
    public:
        /// \brief Create a permutation of the number 1, ... , n
        Permutation(std::size_t n) : std::vector<int>(n), rng_(generator_, dist_)
        {
            permute(n);
        }
        /// \brief Create a permutation of the number 1,...,n
        void permute(unsigned int n)
        {
            if (size() < n)
                resize(n);
            for (unsigned int i = 0; i < n; ++i)
                operator[](i) = i;
            std::random_shuffle(begin(), begin() + n, rng_);
        }
    private:
        /// Mersenne twister random number generator
        boost::mt19937 generator_;
        /// Uniform distribution over integers
        boost::uniform_int<> dist_;
        /// Variate generator
        boost::variate_generator<boost::mt19937&, boost::uniform_int<> > rng_;
    };
}

#endif
