On 09/19/2017 07:54 AM, Dyck, Lionel B. (TRA) wrote:
> I needed a simple sort for the words in a string and came up with this - hope
> it helps others. There are probably better ways to do this so feel free to
> share:
>
> /* ------------------ rexx ------------------------ *
> | Simple bubble sort for words in a string (array) |
> * ------------------------------------------------ */
> string = '10 0 1 9 6 2 4 3'
> do imx = 1 to words(string)-1
> do im = 1 to words(string)
> w1 = word(string,im)
> w2 = word(string,im+1)
> if w1 > w2 then do
> if im > 1
> then lm = subword(string,1,im-1)
> else lm = ''
> rm = subword(string,im+2)
> string = lm w2 w1 rm
> end
> end
> end
> say string
>
>
> --------------------------------------------------------------------------
> Lionel B. Dyck
> Mainframe Systems Programmer - TRA
>
>
For sorting 8 values it's not going to make any difference what sort method is
used, but I wish people would just stop teaching Bubble Sort to
new programmers as a sorting algorithm and teach an Insertion Sort instead.
An Insertion Sort is even easier to explain than a Bubble Sort, not any more
difficult to program, and will always out perform a Bubble Sort, with
the difference becoming more significant for larger N. Of course for really
large N, you should always look at snazzier sorting techniques, but they
are significantly more complex and probably not something one should attempt to
write from memory.
Here is an example of an Insertion Sort for similar data, implemented as a
REXX Procedure on a Linux platform using oorexx. The 10K repetition loop
and use of 50 rather than 8 values was just to get a measurable execution time
comparison on my Linux platform. For 10K sorts of 50 values
Bubble Sort took 33 seconds vs only 4 seconds for same data using the Insertion
Sort.
#!/usr/bin/rexx
/* ------------------ rexx ------------------------ *
| Simple insertion sort for words in a string (array) |
* ------------------------------------------------ */
Do times = 1 To 10000
string = "10 0 200 50 11 32 54 23 13 17 35 14 77 52 92 600 21 45 501 399
27 15 22 425 301" ,
"7 45 65 201 41 37 39 26 19 99 87 73 61 59 95 306 29 48 555 333
22 74 85 444 222"
Call Insert_Sort
End
Say string
Exit
Insert_Sort: Procedure Expose string
n = Words(string)
If n< 2 Then Return
sorted = Word(string,1)
Do i = 2 To n
next = Word(string,i)
Do j = 1 To i-1 /* find where to insert next value among already sorted
values */
If next < Word(sorted,j) Then Do /* must insert before jth value */
If j > 1 Then lm = Subword(sorted,1,j-1)
Else lm = ''
sorted = lm next Subword(sorted,j)
Leave j
End
If j = i-1 Then sorted = sorted next
End
End
string = sorted
Return
--
Joel C. Ewing, Bentonville, AR [email protected]
----------------------------------------------------------------------
For IBM-MAIN subscribe / signoff / archive access instructions,
send email to [email protected] with the message: INFO IBM-MAIN
