https://github.com/dankogai/c-bucketsort

bucketsort - bucket sort that can be used for general purpose
https://github.com/dankogai/c-bucketsort

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bucketsort - bucket sort that can be used for general purpose

• Host: GitHub
• URL: https://github.com/dankogai/c-bucketsort
• Owner: dankogai
• Created: 2012-01-12T21:50:53.000Z (almost 13 years ago)
• Default Branch: master
• Last Pushed: 2012-01-14T19:54:50.000Z (almost 13 years ago)
• Last Synced: 2024-10-31T06:41:49.078Z (14 days ago)
• Language: Perl
• Homepage:
• Size: 140 KB
• Stars: 8
• Watchers: 3
• Forks: 3
• Open Issues: 0
• Metadata Files:
  • Readme: README

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README

        
NAME

    bucketsort - bucket sort

SYNOPSIS

      #include "bucketsort.h"

      int bucketsort(

        void        **base,

        size_t        nmemb,

        keyaccessor_t key,

        indexer_t     idx,

        comparator_t  cmp

      );

DESCRIPTION

    The bucketsort() is an implementations of bucket sort.

  base

    The reference to the array of pointers to the element (or integers whose

    size equals to that of pointer) to be sorted in-place.

  nmemb

    The nember of elements in the array.

  key

    The function pointer which takes the reference to the array element and

    returns the reference to the key.

      void *key(void *element);

    When "NULL" the default function is used which is defined as:

      inline void *identity(void *v)

      {

        return v;

      }

  idx

    The function pointer which takes the reference to the key and the

    recursion level of the caller and returns the integer value between 0

    and 255, which is the bucket id.

    When "NULL" the default function is used which is defined as:

      inline int charAt(void *v, size_t i)

      {

        char *s = (char *) v;

        return s ? strlen(s) > i ? s[i] : 0 : 0;

      };

    In other words, default acts the same as the MSD radix sort with

    variable lengths.

  cmp

    The Function pointer which compares two keys. This is needed to allow

    elements with same keys. Its signature is the same as the one you pass

    to "qsort()", "mergesort()" and "heapsort()" in libc.

    When "NULL", it defaults to:

      inline int stringcmp(void *a, void *b)

      {

        return strcmp(a ? a : "", b ? b : "");

      }

EXAMPLE

    See main.c which is included in the distro.

IMPLEMENTATION DETAILS

    The bucket is implemented as a queue by linked lists. The whole array is

    converted to the linked list before sorted then written back to the

    array. If you like you can use the list sorter directly as:

      list_t bucketsort_l(

        list_t        src,

        size_t        nmemb,

        keyaccessor_t key

        indexer_t     idx,

        comparator_t  cmp

      );

    where:

      typedef struct {

        void *car, *cdr;

      } _cons_t, *list_t;

ACHILLES'S HEEL AND ITS SHIELD

    The obvious drawback of the recursive bucket sort is that it recurses

    deeply when it comes accross data (strings) with long common prefix.

    Given:

      aa..a  # "a" x n

      aa..aa # "a" x (n+1)

    It recurses n times.

    To cope with such cases, "bucketsort()" now falls back to the merge sort

    after "BUCKETSORT_DEPTH", 256 in bucketsort.h. The merge sort used there

    is defined as:

      list_t mergesort_l(

        list_t        src,

        comparator_t  cmp

      );

RETURN VALUES

    The bucketsort() function returns the value 0 if successful; otherwise

    the value -1 is returned and the global variable errno is set to

    indicate the error.

ERRORS

  ENOMEM

    When "bucketsort()" fails to allocate the memory needed to build the

    list, which is exactly twice the size of the original array since each

    element takes two pointers.

SEE ALSO

    sort(3), qsort(3), megesort(3), heapsort(3), radixsort(3)

    

    Engineering Radix Sort

      

      Consequently this program is a generalized verion of the Program A in

      the paper. Their program (and radixsort(1) in 4.4 BSD) is by limiting

      its application to string sorting.