Data commit

Task/Modular-inverse/PureBasic/modular-inverse.basic

@@ -0,0 +1,37 @@
+EnableExplicit
+Declare main()
+Declare.i mi(a.i, b.i)
+
+If OpenConsole("MODULAR-INVERSE")
+  main() : Input() : End
+EndIf
+
+Macro ModularInverse(a, b)
+  PrintN(~"\tMODULAR-INVERSE(" + RSet(Str(a),5) + "," +
+         RSet(Str(b),5)+") = " +
+         RSet(Str(mi(a, b)),5))
+EndMacro
+
+Procedure main()
+  ModularInverse(42, 2017)  ; = 1969
+  ModularInverse(40, 1)     ; = 0
+  ModularInverse(52, -217)  ; = 96
+  ModularInverse(-486, 217) ; = 121
+  ModularInverse(40, 2018)  ; = -1
+EndProcedure
+
+Procedure.i mi(a.i, b.i)
+  Define x.i = 1,
+         y.i = Int(Abs(b)),
+         r.i = 0
+  If y = 1 : ProcedureReturn 0 : EndIf
+  While x < y
+    r = (a * x) % b
+    If r = 1 Or (y + r) = 1
+      Break
+    EndIf
+    x + 1
+  Wend
+  If x > y - 1 : x = -1 : EndIf
+  ProcedureReturn x
+EndProcedure