cosmopolitan/libc/alg/shuffle.h

26 lines
732 B
C

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