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Ingy döt Net 2023-07-01 11:58:00 -04:00
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commit f23f22d71c
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Task/Sorting-algorithms-Quicksort/Red/sorting-algorithms-quicksort.red Normal file
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Red []
;;-------------------------------
;; we have to use function not func here, otherwise we'd have to define all "vars" as local...
qsort: function [list][
;;-------------------------------
if 1 >= length? list [ return list ]
left: copy []
right: copy []
eq: copy [] ;; "equal"
pivot: list/2 ;; simply choose second element as pivot element
foreach ele list [
case [
ele < pivot [ append left ele ]
ele > pivot [ append right ele ]
true [append eq ele ]
]
]
;; this is the last expression of the function, so coding "return" here is not necessary
reduce [qsort left eq qsort right]
]
;; lets test the function with an array of 100k integers, range 1..1000
list: []
loop 100000 [append list random 1000]
t0: now/time/precise ;; start timestamp
qsort list ;; the return value (block) contains the sorted list, original list has not changed
print ["time1: " now/time/precise - t0] ;; about 1.1 sec on my machine
t0: now/time/precise
sort list ;; just for fun time the builtin function also ( also implementation of quicksort )
print ["time2: " now/time/precise - t0]