Last modified on 5 June 2014, at 07:15

Algorithm Implementation/Sorting/Gnome sort

CEdit

void gnome_sort(int *array, int size){ 
   int i, tmp; 
   for(i=1; i<size; ){
       if(array[i-1] <= array[i])
           ++i;
       else{
           tmp = array[i];
           array[i] = array[i-1];
           array[i-1] = tmp;
           --i;
           if(i == 0)
               i = 1;
       }
   }
}

C++Edit

#include <algorithm> // for std::swap
void gnomeSort( int *array, int size )
  {
   for ( int i = 1; i < size; ) {
     if ( array[i-1] <= array[i] ) {
       ++i;
     }
     else {
       std::swap( array[i-1], array[i] );
       --i;
       if ( i == 0 ) {
         i = 1;
       }
     }
   }
}

C++ using bidirectional iteratorsEdit

#include <algorithm> // for std::iter_swap
 
template <typename Iterator>
void gnome_sort(Iterator begin, Iterator end)
{
    Iterator current = begin;
    Iterator before_current;
 
    while (current != end)
    {
        if (current == begin || *before_current <= *current)
        {
            ++current;
        }
        else
        {
            std::iter_swap(before_current, current);
            --current;
        }
        before_current = current;
        --before_current;
    }
}

Optimized C++ using iteratorsEdit

#include <algorithm> // for std::iter_swap
#include <iterator> // for std::advance
 
template <typename Iterator>
void gnome_sort(Iterator begin, Iterator end)
{
    Iterator current = begin;
    Iterator before_current;
    size_t step = 1;
 
    while (current != end)
    {
        if (current == begin || *before_current <= *current)
        {
            std::advance(current, step); // possible leap optimization
            step = 1;
        }
        else
        {
            std::iter_swap(before_current, current);
            --current;
            ++step;
        }
        before_current = current;
        --before_current;
    }
}

The optimized version makes the "gnome" (represented by the 'current' iterator here) leap back to the right i.e. to the place where it needed to swap the flower pots on its farthest reached position so far. This also avoids redundant comparisons. On average the optimization results in cutting the time by one/third on a modern x86 machine. (A wise gnome sort? :). However, the optimization works best if the iterators are random access iterators. Otherwise the algorithm works almost like the non-optimized version - it still avoids redundant comparisons though.

C#Edit

void GnomeSort( int[] array ) 
{ 
  for ( int i = 1, temp_value; i < array.Length; ) 
  { 
    if ( array[i-1] <= array[i] ) 
      i += 1; 
    else 
    { 
      temp_value = array[i-1]; 
      array[i-1] = array[i]; 
      array[i] = temp_value; 
      i -= 1; 
      if ( i == 0 ) 
        i = 1; 
    } 
  } 
}

FORTRANEdit

SUBROUTINE gnome_sort(LIST, LENGTH) 
INTEGER LIST, LENGTH, I, TEMP 
DIMENSION LIST(LENGTH) 
I = 2 
WHILE (I .LE. LENGTH) DO 
  IF ((I .EQ. 1) .OR. (LIST(I-1) .LE. LIST(I))) THEN 
    I = I + 1 
  ELSE 
    TEMP = LIST(I) 
    LIST(I) = LIST(I-1) 
    LIST(I-1) = TEMP 
    I = I - 1 
    IF (I .EQ. 1) THEN 
      I = 2 
    END IF 
  END IF 
END WHILE 
END

JavaEdit

public class GnomeSort { 
   static void gnomeSort( int[] theArray ) { 
      for ( int index = 1; index < theArray.length; ) { 
         if ( theArray[index - 1] <= theArray[index] ) { 
            ++index; 
         } else { 
            int tempVal = theArray[index]; 
            theArray[index] = theArray[index - 1]; 
            theArray[index - 1] = tempVal; 
            --index; 
            if ( index == 0 ) { 
               index = 1; 
            }           
         } 
      } 
   } 
}

JavaScriptEdit

function gnomeSort(sortMe) {
   i=0;
   while (i < sortMe.length) {
      if (i==0||sortMe[i-1] <= sortMe[i]) {
         i++;
      } else {
         tmp=sortMe[i];
         sortMe[i]=sortMe[i-1];
         sortMe[--i]=tmp;
      }
   }
}

LavishScriptEdit

This sorts an scope-accessible index:objectype (IndexName) passed by variable name, sorting by MemberName, which should be a numeric member of objecttype.

method Gnomesort(string IndexName, string MemberName)
{
  variable int i = 1
 
  while ${i} <= ${${IndexName}.Used}
  {
    if ( ${i} == 1 ) || ${${IndexName}[${Math.Calc[${i}-1]}].${MemberName}} <= ${${IndexName}[${i}].${MemberName}}
    {
      i:Inc
    }
    else
    {
      ${IndexName}:Swap[${i}, ${Math.Calc[${i}-1]}]
      i:Dec
    }
  }
}

PerlEdit

sub gnome_sort(@) { 
    my @list  = @_;
    my $size  = scalar(@list);
    my $right = 1;
    while ( $right < $size ) {
        my $left = $right - 1;
        if ( $list[$left] <= $list[$right] ) {
            $right++;
        }
        else {
            @list[ $left, $right ] = @list[ $right, $left ];
            $right-- if $right > 1;
        }
    }
    return @list;
}

PHPEdit

<?php 
function gnome_sort($list) 
{ 
    for ($i = 1; $i < count($list);) 
    { 
        if ($list[$i-1] <= $list[$i]) {$i++;} 
        else 
        { 
            $temp = $list[$i]; 
            $list[$i] = $list[$i-1]; 
            $list[$i-1] = $temp; 
            $i--; 
            if ($i == 0) {$i = 1;} 
        } 
    } 
    return $list; 
}
?>

PythonEdit

def gnomeSort(items):
    i = 0
    n = len(items)
    while i < n:
        if i and items[i] < items[i-1]:
            items[i], items[i-1] = items[i-1], items[i]
            i -= 1
        else:
            i += 1
    return
 
 
def teleportingGnomeSort(items):
    i = j = 0
    n = len(items)
    while i < n:
        if i and items[i] < items[i-1]:
            items[i], items[i-1] = items[i-1], items[i]
            i -= 1
        else:
            if i < j: # teleport!
                i = j
            j = i = i+1
    return

RubyEdit

module GnomeSort
  def self.sort(keys)
    sort!(keys.clone)
  end
 
  def self.sort!(keys)
    i, j = 1, 2
    while i < keys.size
      if keys[i-1] <= keys[i]
        i, j = j, j+1
      else
        keys[i-1], keys[i] = keys[i], keys[i-1]
        i -= 1 if i > 1
      end
    end
    keys
  end
end