September 2017 Update

Task/Quickselect-algorithm/PicoLisp/quickselect-algorithm.l

@@ -0,0 +1,30 @@
+(seed (in "/dev/urandom" (rd 8)))
+(de swapL (Lst X Y)
+   (let L (nth Lst Y)
+      (swap
+         L
+         (swap (nth Lst X) (car L)) ) ) )
+(de partition (Lst L R P)
+   (let V (get Lst P)
+      (swapL Lst R P)
+      (for I (range L R)
+         (and
+            (> V (get Lst I))
+            (swapL Lst L I)
+            (inc 'L) ) )
+      (swapL Lst L R)
+      L ) )
+(de quick (Lst N L R)
+   (default L (inc N)  R (length Lst))
+   (if (= L R)
+      (get Lst L)
+      (let P (partition Lst L R (rand L R))
+         (cond
+            ((= N P) (get Lst N))
+            ((> P N) (quick Lst N L P))
+            (T (quick Lst N P R)) ) ) ) )
+(let Lst (9 8 7 6 5 0 1 2 3 4)
+   (println
+      (mapcar
+         '((N) (quick Lst N))
+         (range 0 9) ) ) )