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Task/Quickselect-algorithm/Icon/quickselect-algorithm.icon

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+procedure main(A)
+    every writes(" ",select(1 to *A, A, 1, *A)|"\n")
+end
+
+procedure select(k,A,min,max)
+    repeat {
+        pNI := partition(?(max-min)+min, A, min, max)
+        pD := pNI - min + 1
+        if pD = k then return A[pNI]
+        if k < pD then max := pNI-1
+        else (k -:= pD, min := pNI+1)
+        }
+end
+
+procedure partition(pivot,A,min,max)
+    pV := (A[max] :=: A[pivot])
+    sI := min
+    every A[i := min to max-1] <= pV do (A[sI] :=: A[i], sI +:= 1)
+    A[max] :=: A[sI]
+    return sI
+end