random.h

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 * Copyright 2008-2009  Marius Muja (mariusm@cs.ubc.ca). All rights reserved.
 * Copyright 2008-2009  David G. Lowe (lowe@cs.ubc.ca). All rights reserved.
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#ifndef RTABMAP_FLANN_RANDOM_H
#define RTABMAP_FLANN_RANDOM_H

#include <algorithm>
#include <cstdlib>
#include <cstddef>
#include <vector>

#include "rtflann/general.h"

namespace rtflann
{

inline void seed_random(unsigned int seed)
{
    srand(seed);
}

/*
 * Generates a random double value.
 */
inline double rand_double(double high = 1.0, double low = 0)
{
    return low + ((high-low) * (std::rand() / (RAND_MAX + 1.0)));
}

inline int rand_int(int high = RAND_MAX, int low = 0)
{
    return low + (int) ( double(high-low) * (std::rand() / (RAND_MAX + 1.0)));
}


class RandomGenerator
{
public:
    ptrdiff_t operator() (ptrdiff_t i) { return rand_int(i); }
};


class UniqueRandom
{
    std::vector<int> vals_;
    int size_;
    int counter_;

public:
    UniqueRandom(int n)
    {
        init(n);
    }

    void init(int n)
    {
        static RandomGenerator generator;
        // create and initialize an array of size n
        vals_.resize(n);
        size_ = n;
        for (int i = 0; i < size_; ++i) vals_[i] = i;

        // shuffle the elements in the array
        std::random_shuffle(vals_.begin(), vals_.end(), generator);

        counter_ = 0;
    }

    int next()
    {
        if (counter_ == size_) {
            return -1;
        }
        else {
            return vals_[counter_++];
        }
    }
};

}

#endif //FLANN_RANDOM_H