Initial data commit

Task/Greatest-common-divisor/Pascal/greatest-common-divisor-1.pas

@@ -0,0 +1,26 @@
+PROGRAM EXRECURGCD.PAS;
+
+{$IFDEF FPC}
+    {$mode objfpc}{$H+}{$J-}{R+}
+{$ELSE}
+    {$APPTYPE CONSOLE}
+{$ENDIF}
+
+(*)
+    Free Pascal Compiler version 3.2.0 [2020/06/14] for x86_64
+    The free and readable alternative at C/C++ speeds
+    compiles natively to almost any platform, including raspberry PI
+(*)
+
+FUNCTION gcd_recursive(u, v: longint): longint;
+
+    BEGIN
+        IF ( v = 0 ) THEN Exit ( u ) ;
+        result := gcd_recursive ( v, u MOD v ) ;
+    END;
+
+BEGIN
+
+    WriteLn ( gcd_recursive ( 231, 7 ) ) ;
+
+END.

Task/Greatest-common-divisor/Pascal/greatest-common-divisor-2.pas

@@ -0,0 +1,12 @@
+function gcd_iterative(u, v: longint): longint;
+  var
+    t: longint;
+  begin
+    while v <> 0 do
+    begin
+      t := u;
+      u := v;
+      v := t mod v;
+    end;
+    gcd_iterative := abs(u);
+  end;

Task/Greatest-common-divisor/Pascal/greatest-common-divisor-3.pas

@@ -0,0 +1,40 @@
+function gcd_binary(u, v: longint): longint;
+  var
+    t, k: longint;
+  begin
+    u := abs(u);
+    v := abs(v);
+    if u < v then
+    begin
+      t := u;
+      u := v;
+      v := t;
+    end;
+    if v = 0 then
+      gcd_binary := u
+    else
+    begin
+      k := 1;
+      while (u mod 2 = 0) and (v mod 2 = 0) do
+      begin
+        u := u >> 1;
+        v := v >> 1;
+	k := k << 1;
+      end;
+      if u mod 2 = 0 then
+        t := u
+      else
+        t := -v;
+      while t <> 0 do
+      begin
+        while t mod 2 = 0 do
+          t := t div 2;
+        if t > 0 then
+          u := t
+        else
+          v := -t;
+        t := u - v;
+      end;
+      gcd_binary := u * k;
+    end;
+  end;

Task/Greatest-common-divisor/Pascal/greatest-common-divisor-4.pas

@@ -0,0 +1,6 @@
+Program GreatestCommonDivisorDemo(output);
+begin
+  writeln ('GCD(', 49865, ', ', 69811, '): ', gcd_iterative(49865, 69811), ' (iterative)');
+  writeln ('GCD(', 49865, ', ', 69811, '): ', gcd_recursive(49865, 69811), ' (recursive)');
+  writeln ('GCD(', 49865, ', ', 69811, '): ', gcd_binary   (49865, 69811), ' (binary)');
+end.