24 lines
719 B
C
24 lines
719 B
C
#ifndef COSMOPOLITAN_LIBC_RAND_SHUFFLE_H_
|
|
#define COSMOPOLITAN_LIBC_RAND_SHUFFLE_H_
|
|
#if !(__ASSEMBLER__ + __LINKER__ + 0)
|
|
#include "libc/bits/xchg.h"
|
|
|
|
/**
|
|
* 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()
|
|
*/
|
|
#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_ */
|