Sorting algorithms/Bubble sort

Sorting algorithms/Bubble sort
You are encouraged to solve this task according to the task description, using any language you may know.

Sorting Algorithm
This is a sorting algorithm.   It may be applied to a set of data in order to sort it.     For comparing various sorts, see compare sorts.   For other sorting algorithms,   see sorting algorithms,   or:

O(n logn) sorts

Heap sort | Merge sort | Patience sort | Quick sort

O(n log²n) sorts
Shell Sort

O(n²) sorts
Bubble sort | Cocktail sort | Cocktail sort with shifting bounds | Comb sort | Cycle sort | Gnome sort | Insertion sort | Selection sort | Strand sort

other sorts
Bead sort | Bogo sort | Common sorted list | Composite structures sort | Custom comparator sort | Counting sort | Disjoint sublist sort | External sort | Jort sort | Lexicographical sort | Natural sorting | Order by pair comparisons | Order disjoint list items | Order two numerical lists | Object identifier (OID) sort | Pancake sort | Quickselect | Permutation sort | Radix sort | Ranking methods | Remove duplicate elements | Sleep sort | Stooge sort | [Sort letters of a string] | Three variable sort | Topological sort | Tree sort

In this task, the goal is to sort an array of elements using the bubble sort algorithm. The elements must have a total order and the index of the array can be of any discrete type. For languages where this is not possible, sort an array of integers.

Algorithm

The bubble sort is generally considered to be the simplest sorting algorithm. Because of its simplicity and ease of visualization, it is often taught in introductory computer science courses. Because of its abysmal performance, it is never used anywhere else.

The bubble sort works by passing sequentially over a list, comparing each value to the one immediately after it. If the first value is greater than the second, their positions are switched. Over a number of passes, at most equal to the number of elements in the list, all of the values drift into their correct positions. (Large values "bubble" rapidly toward the end, pushing others down around them.) A boolean variable is used to track whether any changes have been made in the current pass; when a pass completes without changing anything, the algorithm exits.

This can be expressed in pseudocode as follows (assuming 1-based indexing):

repeat forever
    set hasChanged to false
    repeat with index from 1 to (itemCount - 1)
        if (item at index) > (item at (index + 1))
            swap (item at index) with (item at (index + 1))
            set hasChanged to true
    if hasChanged is false
        exit

Examples

Ada

Compiler: GCC 4.1.2

generic
 type Element is private;
 with function "=" (E1, E2 : Element) return Boolean is <>;
 with function "<" (E1, E2 : Element) return Boolean is <>;
 type Index is (<>);
 type Arr is array (Index range <>) of Element;
procedure Bubble_Sort (A : in out Arr);

procedure Bubble_Sort (A : in out Arr) is
 Finished : Boolean;
 Temp     : Element;
begin
 loop
  Finished := True;
  for J in A'First .. Index'Pred (A'Last) loop
   if A (Index'Succ (J)) < A (J) then
    Finished := False;
    Temp := A (Index'Succ (J));
    A (Index'Succ (J)) := A (J);
    A (J) := Temp;
   end if;
  end loop;
  exit when Finished;
 end loop;
end Bubble_Sort;

--  Example of usage:
with Ada.Text_IO; use Ada.Text_IO;
with Bubble_Sort;
procedure Main is
 type Arr is array (Positive range <>) of Integer;
 procedure Sort is new
  Bubble_Sort
   (Element => Integer,
    Index   => Positive,
    Arr     => Arr);
 A : Arr := (1, 3, 256, 0, 3, 4, -1);
begin
 Sort (A);
 for J in A'Range loop
  Put (Integer'Image (A (J)));
 end loop;
 New_Line;
end Main;

C++

Compiler: g++ 4.0.2

#include <iostream>
#include <algorithm>

template< typename ARRAY_TYPE, typename INDEX_TYPE >
void
bubble_sort( ARRAY_TYPE array[], INDEX_TYPE size )
{
 bool done = false ;
 
 while( !done )
 {
  done = true ;
  for( INDEX_TYPE i = 0 ; i < size - 1 ; i++ )
  {
   if( array[i] > array[i+1] )
   {
    done = false ;
    ARRAY_TYPE temp = array[i+1] ;
    array[i+1] = array[i] ;
    array[i] = temp ;
   }
  }
 }
}

template< typename TYPE >
void
print( TYPE val )
{
 std::cout << val << " " ;
}

int
main( int argc, char* argv[] )
{
 int array[] = { 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 } ;
 bubble_sort( array, 10 ) ;
 std::for_each( &array[0], &array[10], print<int> ) ;
 std::cout << std::endl ;
 
 //But in real life...
 int data[] = { 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 } ;
 std::sort( data, data+10 ) ;
 std::for_each( data, data+10, print<int> ) ;
 std::cout << std::endl ;
}

Forth

Sorts the 'cnt' cells stored at 'addr'. Uses forth local variables for clarity.

: bubble { addr cnt -- }
  cnt 0 DO
    addr cnt i - cells bounds DO
      i 2@ > if i 2@ swap i 2! then
    cell +LOOP 
  LOOP ;

This is the same algorithm done without the local variables:

: bubble ( addr cnt -- )
  dup 0 DO
    2dup i - cells bounds DO
      i 2@ > if i 2@ swap i 2! then
    cell +LOOP 
  LOOP ;

Haskell

This version checks for changes in a separate step for simplicity, because Haskell has no variables to track them with.

bsort :: Ord a => [a] -> [a]
bsort s = case _bsort s of
               t | t == s    -> t
                 | otherwise -> bsort t
  where _bsort (x:x2:xs) | x > x2    = x2:(_bsort (x:xs))
                         | otherwise = x:(_bsort (x2:xs))
        _bsort s = s

This version uses the polymorphic Maybe type to designate unchanged lists. (The type signature of _bsort is now Ord a => [a] -> Maybe [a].) It is slightly faster than the previous one.

bsort :: Ord a => [a] -> [a]
bsort s = case _bsort s of
               Nothing -> s
               Just s2 -> bsort s2
  where _bsort (x:x2:xs) | x > x2    = case _bsort (x:xs) of
                                            Nothing  -> Just $ x2:x:xs
                                            Just xs2 -> Just $ x2:xs2
                         | otherwise = case _bsort (x2:xs) of
                                            Nothing  -> Nothing
                                            Just xs2 -> Just $ x:xs2
        _bsort _ = Nothing

Perl

Interpreter: perl 5.8.8

 # Sorts an array in place and returns a copy
 sub bubble_sort (@) {
     my $len = @_ - 1;
     for my $i (0..$len-1){
         for my $j ($i+1..$len){
             @_[$i,$j] = @_[$j,$i] if $_[$j] lt $_[$i];
         }
     }
     return @_;
 }

 # Usage
 @a = qw/G F C A B E D/; 
 bubble_sort(@a);

Alternate "Long Hand" Perl Method

  sub Bubble_Sort {
     my @list = @_;
     my $temp = 0;
     my $done = 0;
     my $elements = $#list + 1;
  
     while ($done == 0) {
        $done = 1;
        for (my $i=0;$i<$elements;$i++) {
           if ($list[$i] > $list[$i+1] && ($i + 1) < $elements) {
              $done = 0;
              $temp = $list[$i];
              $list[$i] = $list[$i+1];
              $list[$i+1] = $temp;
           }
        }
     }
  
     return @list;
  }

  #usage
  my @test = (1, 3, 256, 0, 3, 4, -1);
  print join(",",Bubble_Sort(@test));

Python

def bubblesort(seq):
    for i in xrange(1, len(seq)):
        for j in range(len(seq) - i):
            if seq[j] > seq[j+1]:
                seq[j], seq[j+1] = seq[j+1], seq[j]

data = [3, 78, 4, 23, 6, 8, 6]
bubblesort(data)
print data # [3, 4, 6, 6, 8, 23, 78]

Ruby

Although the native Ruby sort method for Arrays if much faster (O(n*log(n)) versus O(n**2)), you can find a Ruby version of Bubble sort hereunder. It adds the bubblesort! method to the Array object. Below are two different methods that show four different iterating constructs in ruby.

 class Array
   def bubblesort1!
     length.times do |j|
       for i in 1...(length - j)
         if self[i] < self[i - 1]
           self[i], self[i - 1] = self[i - 1], self[i]
         end
       end
     end
   
     return self
   end

   def bubblesort2!
     each_index do |index|
       (length - 1).downto( index ) do |i|
         a, b = self[i-1], self[i]
         a, b = b, a if b < a
       end
     end
   
     return self
   end
 end

 puts [3, 78, 4, 23, 6, 8, 6].bubblesort1!
 # => [3, 4, 6, 6, 8, 23, 78]