THANK YOU FOR WRITING THIS WHOEVER DID!!!

Does the sample implementation given depend on the endianness used by the computer? I'm not quite sure what exactly the >> operator does. --AxelBoldt

#### Sample radix sort of an array of integers

Does the sample implementation given depend on the endianness used by the computer? I'm not quite sure what exactly the >> operator does. --AxelBoldt

The value of x >> y is floor(x / 2^{y}), provided x and y are non-negative, and y is not too big. So it doesn't depend on endianness in this case. But if x is negative, then the value is undefined, so this is a problem. Another problem with the code in the article is that it assumes that CHAR_BIT is 8. --Zundark, 2001 Dec 11

So maybe we should make them unsigned ints to take care of the sign issue? Is there a clean way to deal with the CHAR_BIT thingy?

I think we should probably have an implementation that deals with keys that are (arbitrary length) strings, since that seems to be the more interesting case. --AxelBoldt

I changed the int array to unsigned. The CHAR_BIT thing is more problematic, so I just added a note pointing it out. On most compilers for desktop computers CHAR_BIT is 8, so this isn't too bad a restriction. --Zundark, 2001 Dec 11

Having looked at it more closely, I see that it has more serious problems than those mentioned above, so I've moved it here until it gets fixed. --Zundark, 2001 Dec 11

This sample implementation is written in the C programming language.

/* * This implementation sorts one byte at a time, so 32 bit integers get sorted in 4 passes. * It uses a simplified bucket sort to sort on each byte, which requires O(n) memory. * It assumes that CHAR_BIT is 8. */ struct listnode /* a simple linked list data structure */ { /* used for the bucket sort */ unsigned val; struct listnode * next; }; void sort(unsigned * array, int length) { int i, j; unsigned char key; struct listnode nodes[length]; /* an array of preallocated listnodes */ struct listnode * buckets[0x100]; /* the buckets for the bucket sort */ memset(buckets, 0, 0x100 * sizeof(struct listnode *)); /* zero the memory */ for(i = 0; i < sizeof(unsigned); i++) /* iterate over the bytes in an unsigned int */ { for(j = 0; j < length; j++) /* iterate over the array */ { key = (char)((array[j] >> (i * 8)) & 0xFF); /* grab the byte */ nodes[j].val = array[j]; /* put the byte in the bucket */ nodes[j].next = buckets[key]; buckets[key] = &(nodes[j]); } j = length - 1; for(key = 0xFF; key >= 0; key--) /* loop over the buckets */ while(buckets[key] != 0) { array[j] = buckets[key]->val; /* pull the values out of the buckets */ buckets[key] = buckets[key]->next; /* and put them back in the array */ j--; } } }