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split reversible Fisher Yates shuffle into two

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Ahmet Inan 2023-05-11 08:59:49 +02:00
commit 8a055ac2b2
1 changed files with 15 additions and 9 deletions
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@ -11,24 +11,30 @@ Copyright 2023 Ahmet Inan <inan@aicodix.de>
namespace CODE { namespace CODE {
template <int SIZE> template <int SIZE>
class ReversibleFisherYatesShuffle struct FisherYatesShuffle
{
template <typename TYPE>
void operator()(TYPE *array)
{
CODE::Xorshift32 prng;
for (int i = 0; i < SIZE-1; ++i)
std::swap(array[i], array[i + prng() % (SIZE - i)]);
}
};
template <int SIZE>
class ReverseFisherYatesShuffle
{ {
int seq[SIZE-1]; int seq[SIZE-1];
public: public:
ReversibleFisherYatesShuffle() ReverseFisherYatesShuffle()
{ {
CODE::Xorshift32 prng; CODE::Xorshift32 prng;
for (int i = 0; i < SIZE-1; ++i) for (int i = 0; i < SIZE-1; ++i)
seq[i] = i + prng() % (SIZE - i); seq[i] = i + prng() % (SIZE - i);
} }
template <typename TYPE> template <typename TYPE>
void forward(TYPE *array) void operator()(TYPE *array)
{
for (int i = 0; i < SIZE-1; ++i)
std::swap(array[i], array[seq[i]]);
}
template <typename TYPE>
void reverse(TYPE *array)
{ {
for (int i = SIZE-2; i >= 0; --i) for (int i = SIZE-2; i >= 0; --i)
std::swap(array[i], array[seq[i]]); std::swap(array[i], array[seq[i]]);