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Task/Sorting-algorithms-Quicksort/CoffeeScript/sorting-algorithms-quicksort.coffeescript

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+# This shows quicksort-in-place.
+quicksort = (a) ->
+  swap = (i, j) ->
+    return if i == j
+    [a[i], a[j]] = [a[j], a[i]]
+
+  divide = (v, start, end) ->
+    first_big = start
+    j = start
+    while j <= end
+      if a[j] < v
+        swap first_big, j
+        first_big += 1
+      j += 1
+    first_big
+
+  partition = (start, end) ->
+    v = a[end]
+    first_big = divide v, start, end-1
+    swap first_big, end
+    first_big
+
+  qs = (start, end) ->
+    return if start >= end
+    m = partition start, end
+    qs start, m-1
+    qs m+1, end
+
+  qs 0, a.length - 1
+
+# test
+do ->
+  a = [1, 3, 5, 7, 9, 8, 6, 4, 2, 0, 3.5]
+  quicksort(a)
+  console.log a # [ 0, 1, 2, 3, 3.5, 4, 5, 6, 7, 8, 9 ]