Queue - Data Structures

[kevin]

PlayBASIC Code: [Select]

; *=-------------------------------------------------------------------------=*
;
;   This example shows how you can roll some functions to treat arrays like
; a QUEUE.  In this example were using a 1D integer array, but you could use
; floats, strings or even typed arrays if you wanted.
;
;  What is a QUEUE ?
;  =================
;
;   Conceptually, QUEUE's are simply a data storage method that allows adding
;  and removing elements in a particular order. Every time an element is added,
;  it goes on the end of the queue, the only elements that can be removed is the
;  element that was at the  FRONT of queue.
;
;   Consequently, a queue is said to have
;  "first in first out" behavior (or "last in, last out"). The first item added
;  will be the first item removed from it.
;
;     If if add the numbers 30,10,50..  They'd come back in the order they
;  were adding.  Ie 30-> then 10-> then 50
;
; *=-------------------------------------------------------------------------=*


 Dim MyQueue(0)

 Print "Adding Data to Queue"
 For lp=0 to 10
   ; grab a random value to store on our MyQueue() array
  ThisValue=rnd(1000)  

   ; display the value so we can see it
     print ThisValue

   ; add item to our queue
     AddToQueue(MyQueue(),ThisValue)
 next



 SetCursor 0,200
 print "Queue CONTENTS:"
 print ShowQueue(MyQueue())


; Display the values from our queue
  setcursor 0,250
  Print "Queue values"

  For lp=1 to QueueSize(MyQueue())
     Print NextInQueue(MyQueue())  
  next


; show the contents after popping them
   setcursor 0,420
   print "Queue CONTENTS:"
   print ShowQueue(MyQueue())


Sync
waitkey



; =-----------------------------------------------------------------=*
;            Get the Size of this QUE array
; =-----------------------------------------------------------------=*


FUnction QueueSize(Array())
  Size=GetArrayElements(Array(),1)
EndFunction Size




; =-----------------------------------------------------------------=*
;            Push a Integer value onto our QUEUE array
; =-----------------------------------------------------------------=*


Function AddToQueue(Array(),ThisValue) 
   ; Get the current size of this array plus 1
  Size=GetArrayElements(Array(),1)+1

   ; redim it (resize) so it's one element bigger
  redim Array(size)  

   ; insert the new element at the end of array
  array(Size)=ThisValue
EndFunction



; =-----------------------------------------------------------------=*
;             Read the element at the head of the que
; =-----------------------------------------------------------------=*

Function NextInQueue(Array())
   ; Get the size of the array
  Size=GetArrayElements(Array(),1)

   ; check if there's at least 1 item in the queue
  if size>0

  ; grab the FIRST item at array index #1
     ThisValue=Array(1)

  ; copy all the following cells Up.  So now element
  ; 2 is in element 1's position and so on
     CopyArrayCells  array(),1,1,array(),0,1,size

        ; reduce the arrays size by 1 element 
     redim Array(size-1)  
  endif
EndFunction ThisValue



; =-----------------------------------------------------------------=*
;        Build a string of the Queue's contents for displaying
; =-----------------------------------------------------------------=*

Function ShowQueue(Array())
  Size=GetArrayElements(Array(),1)
  if size>0
     for lp=1 to size
    s$=s$+str$(Array(lp))
    if lp<>size then s$=s$+","
     next
  else
     S$="Queue Is Empty"
  endif
EndFunction s$

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[Adaz]

I've never heard of Que, is this different than Queue?

[thaaks]

No, it's not. A que is a queue is a queue.

I'm off, taking the last queue as a cue for some pool billiard  ;D