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23 lines
730 B
C
23 lines
730 B
C
#ifndef COSMOPOLITAN_LIBC_RAND_SHUFFLE_H_
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#define COSMOPOLITAN_LIBC_RAND_SHUFFLE_H_
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#include "libc/intrin/xchg.internal.h"
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#if !(__ASSEMBLER__ + __LINKER__ + 0)
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/**
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* Fisher-Yates shuffle.
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*
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* @param R is a function like rand() → ≥0
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* @param A is a typed array
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* @param n is the number of items in A
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* @see ARRAYLEN()
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*/
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#define shuffle(R, A, n) \
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do { \
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autotype(A) Array = (A); \
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for (size_t i = (n)-1; i >= 1; --i) { \
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xchg(&Array[i], &Array[R() % (i + 1)]); \
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} \
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} while (0)
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#endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
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#endif /* COSMOPOLITAN_LIBC_RAND_SHUFFLE_H_ */
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