September 2017 Update

Task/Permutations/FreeBASIC/permutations.freebasic

@@ -0,0 +1,52 @@
+' version 07-04-2017
+' compile with: fbc -s console
+
+' Heap's algorithm non-recursive
+Sub perms(n As Long)
+
+    Dim As ULong i, j, count = 1
+    Dim As ULong a(0 To n -1), c(0 To n -1)
+
+    For j = 0 To n -1
+        a(j) = j +1
+        Print a(j);
+    Next
+    Print " ";
+
+    i = 0
+    While i < n
+        If c(i) < i Then
+            If (i And 1) = 0 Then
+                Swap a(0), a(i)
+            Else
+                Swap a(c(i)), a(i)
+            End If
+            For j = 0 To n -1
+                Print a(j);
+            Next
+            count += 1
+            If count = 12 Then
+                Print
+                count = 0
+            Else
+                Print " ";
+            End If
+            c(i) += 1
+            i = 0
+        Else
+            c(i) = 0
+            i += 1
+        End If
+    Wend
+
+End Sub
+
+' ------=< MAIN >=------
+
+perms(4)
+
+' empty keyboard buffer
+While Inkey <> "" : Wend
+Print : Print "hit any key to end program"
+Sleep
+End