September 2017 Update

Task/Sorting-algorithms-Quicksort/Simula/sorting-algorithms-quicksort.simula

@@ -0,0 +1,30 @@
+PROCEDURE QUICKSORT(A); REAL ARRAY A;
+BEGIN
+
+    PROCEDURE QS(A, FIRST, LAST); REAL ARRAY A; INTEGER FIRST, LAST;
+    BEGIN
+        INTEGER LEFT, RIGHT;
+        LEFT := FIRST; RIGHT := LAST;
+        IF RIGHT - LEFT + 1 > 1 THEN
+        BEGIN
+            REAL PIVOT;
+            PIVOT := A((LEFT + RIGHT) // 2);
+            WHILE LEFT <= RIGHT DO
+            BEGIN
+                WHILE A(LEFT) < PIVOT DO LEFT := LEFT + 1;
+                WHILE A(RIGHT) > PIVOT DO RIGHT := RIGHT - 1;
+                IF LEFT <= RIGHT THEN
+                BEGIN
+                    REAL SWAP;
+                    SWAP := A(LEFT); A(LEFT) := A(RIGHT); A(RIGHT) := SWAP;
+                    LEFT := LEFT + 1; RIGHT := RIGHT - 1;
+                END;
+            END;
+            QS(A, FIRST, RIGHT);
+            QS(A, LEFT, LAST);
+        END;
+    END QS;
+
+    QS(A, LOWERBOUND(A, 1), UPPERBOUND(A, 1));
+
+END QUICKSORT;