shuffleArray

C

Public Domain

Randomly rearrange the contents of an array

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Tags:

array C random randomize shuffle sort 
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#include <stdlib.h>
#include <string.h>

/* ``shuffleArray(deck, elemSize, len)'' randomly reorganizes an
 * array of `len' items, each `elemSize' bytes in size, located at `deck'.
 * It returns `deck' on success, NULL if an error occurred. */

void* shuffleArray(void* restrict deck, size_t elemSize, size_t len) {
 if (!deck || elemSize < 1 || len < 1) return NULL;
 void* restrict buffer = malloc(elemSize);
 if (!buffer) return NULL;
 for (int i=0; i<len; i++) {
  int bavi = random() % (len-i) + i;
  if (bavi != i) {
   memcpy(buffer, deck + elemSize * i, elemSize);
   memcpy(deck + elemSize * i, deck + elemSize * bavi, elemSize);
   memcpy(deck + elemSize * bavi, buffer, elemSize);
  }
 }
 free(buffer);
 return deck;
}