Cocktail Sort - Pseudocode

Pseudocode

The simplest form of cocktail sort goes through the whole list each time:

procedure cocktailSort( A : list of sortable items ) defined as: do swapped := false for each i in 0 to length( A ) - 2 do: if A > A then // test whether the two elements are in the wrong order swap( A, A ) // let the two elements change places swapped := true end if end for if swapped = false then // we can exit the outer loop here if no swaps occurred. break do-while loop end if swapped := false for each i in length( A ) - 2 to 0 do: if A > A then swap( A, A ) swapped := true end if end for while swapped // if no elements have been swapped, then the list is sorted end procedure

The first rightward pass will shift the largest element to its correct place at the end, and the following leftward pass will shift the smallest element to its correct place at the beginning. The second complete pass will shift the second largest and second smallest elements to their correct places, and so on. After i passes, the first i and the last i elements in the list are in their correct positions, and do not need to be checked. By shortening the part of the list that is sorted each time, the number of operations can be halved (see bubble sort).

procedure cocktailSort( A : list of sortable items ) defined as: // `begin` and `end` marks the first and last index to check begin := -1 end := length( A ) - 2 do swapped := false // increases `begin` because the elements before `begin` are in correct order begin := begin + 1 for each i in begin to end do: if A > A then swap( A, A ) swapped := true end if end for if swapped = false then break do-while loop end if swapped := false // decreases `end` because the elements after `end` are in correct order end := end - 1 for each i in end to begin do: if A > A then swap( A, A ) swapped := true end if end for while swapped end procedure