~ Quicksort using pointers
#S,a;                          ~ Numbers to be sorted are stored
                               ~ in the array "a"
$S "Enter numbers to be sorted (0 terminates):!"
   1% 1 - p:                   ~ Initialize pointer to array
   ( ? n: n. 0 > ^             ~ Read a number and check it
      p. 1 + p: n.p.: )        ~ Increment pointer and store number
   "!"
   #Q,1%,p.;                   ~ Sort the array
   "Sorted array:!"
   1% q:                       ~ Set pointer for output
   ( q.. ! " "                 ~ Display one number
      q. p. < ^                ~ Check finished
      q. 1 + q: )              ~ Increment pointer and loop
   "!" @
$Q 1% i:                       ~ Set pointers to beginning,
   2% j:                       ~     end,
   i. j. + 2 / . m:            ~        and middle component
   ( ( i.. m. < ^
      i. 1 + i: )
   ( m. j.. < ^
      j. 1 - j: )
   i. j. 1 + <
      [ i.. j.. i.: j.:        ~ Swap array components
         i. 1 + i:             ~ Update pointers
         j. 1 - j: ]
   i. j. 1 + < ^ )
   1% j. <
      [ #Q,1%,j.; ]            ~ Sort left end
   i. 2% <
      [ #Q,i.,2%;] @           ~ Sort right end