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39 lines
624 B
C++
39 lines
624 B
C++
/*
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Reversible permutations
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Copyright 2023 Ahmet Inan <inan@aicodix.de>
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*/
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#pragma once
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#include "xorshift.hh"
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namespace CODE {
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template <int SIZE>
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class ReversibleFisherYatesShuffle
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{
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int seq[SIZE-1];
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public:
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ReversibleFisherYatesShuffle()
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{
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CODE::Xorshift32 prng;
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for (int i = 0; i < SIZE-1; ++i)
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seq[i] = i + prng() % (SIZE - i);
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}
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template <typename TYPE>
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void forward(TYPE *array)
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{
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for (int i = 0; i < SIZE-1; ++i)
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std::swap(array[i], array[seq[i]]);
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}
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template <typename TYPE>
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void reverse(TYPE *array)
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{
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for (int i = SIZE-2; i >= 0; --i)
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std::swap(array[i], array[seq[i]]);
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}
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};
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}
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