"Michael McGarry" <mi*************@gmail.comwrote in message
news:11**********************@m79g2000cwm.googlegr oups.com...
Hi,
Please excuse me if this is not the right forum for this question. I
would like to create a random permutation of a list of numbers. How can
I do this in C?
I was just going to draw a number from 1 to n. n is the number of items
in the list and place the items in a new list in the order that their
index is drawn from the random number generator. Is there a library
function to do this?
It is trivial to make it. There are quality bugs in the code below.
#include <stdlib.h>
void shuffle(int *arr, int arr_size)
{
int tmp;
size_t i;
for (i = 0; i < arr_size; i++) {
int rval = rand() % arr_size;
tmp = arr[i];
arr[i] = arr[rval];
arr[rval] = tmp;
}
}
#ifdef UNIT_TEST
#include <stdio.h>
typedef enum suite {
club=1, heart=2, diamond=4, spade=8
} suite;
typedef enum face {
deuce = 16, trey=32, four=64, five=128, six=256, seven=512,
eight=1024,
nine=2048, ten=4096, jack=8192, queen=16384, king=32768, ace=65536
} face;
int dequeue[52];
void decipher_face(int input)
{
switch ((input >4) << 4) {
case deuce:
printf("deuce ");
break;
case trey:
printf("trey ");
break;
case four:
printf("four ");
break;
case five:
printf("five ");
break;
case six:
printf("six ");
break;
case seven:
printf("seven ");
break;
case eight:
printf("eight ");
break;
case nine:
printf("nine ");
break;
case ten:
printf("ten ");
break;
case jack:
printf("jack ");
break;
case queen:
printf("queen ");
break;
case king:
printf("king ");
break;
case ace:
printf("ace ");
break;
default:
printf("unknown ");
break;
}
}
void decipher_suite(int input)
{
switch (input & 0xF) {
case club:
puts("of clubs.");
break;
case heart:
puts("of hearts.");
break;
case diamond:
puts("of diamonds.");
break;
case spade:
puts("of spades.");
break;
default:
puts("unknown ");
break;
}
}
int main(void)
{
suite s_index;
face f_index;
size_t index;
int where = 0;
/* Make the list... */
puts("\nMake the list...");
for (s_index = club; s_index <= spade; s_index<<=1)
for (f_index = deuce; f_index <= ace; f_index<<=1) {
dequeue[where++] = (size_t) s_index + (size_t) f_index;
}
/* Dump the original list */
puts("\nDump the original list...");
for (index = 0; index < sizeof dequeue / sizeof dequeue[0];
index++)
{
decipher_face(dequeue[index]);
decipher_suite(dequeue[index]);
}
/* Shuffle the list... */
puts("\nShuffle the list...");
shuffle(dequeue, sizeof dequeue / sizeof dequeue[0]);
/* Dump the shuffled list */
puts("\nDump the shuffled list...");
for (index = 0; index < sizeof dequeue / sizeof dequeue[0];
index++)
{
decipher_face(dequeue[index]);
decipher_suite(dequeue[index]);
}
return 0;
}
#endif
