DivideLeft, DivideRight

ftreap.pas

@@ -40,7 +40,10 @@   generic TTreapNode<T> = class
     class function Meld(l, r: TTreapNode): TTreapNode;
 
     (* Divides tree into two trees. Where @code(Max(l) <= k). *)
-    class procedure Divide(node: TTreapNode; k: T; var l, r: TTreapNode);
+    class procedure DivideRight(node: TTreapNode; k: T; var l, r: TTreapNode);
+
+    (* Divides tree into two trees. Where @code(Max(l) < k). *)
+    class procedure DivideLeft(node: TTreapNode; k: T; var l, r: TTreapNode);
 
     (* Divides tree into two trees. Where @code(Size(l) = pos). *)
     class procedure DivideAt(node: TTreapNode; const pos: SizeUInt;
@@ -214,8 +217,7 @@ class procedure TTreapNode.DivideAt(node: TTreapNode; const pos: SizeUInt;
   UpdateSize(node)
 end;
 
-// DivideRight
-class procedure TTreapNode.Divide(node: TTreapNode; k: T; var l, r: TTreapNode);
+class procedure TTreapNode.DivideRight(node: TTreapNode; k: T; var l, r: TTreapNode);
 begin
   if node = nil then
   begin
@@ -225,13 +227,34 @@ class procedure TTreapNode.Divide(node: TTreapNode; k: T; var l, r: TTreapNode);
   end;
   if k < node.FKey then
   begin
-    Divide(node.FLeft, k, l, node.FLeft);
+    DivideRight(node.FLeft, k, l, node.FLeft);
     r := node;
   end
   else
   begin
-    Divide(node.FRight, k, node.FRight, r);
+    DivideRight(node.FRight, k, node.FRight, r);
+    l := node;
+  end;
+  UpdateSize(node);
+end;
+
+class procedure TTreapNode.DivideLeft(node: TTreapNode; k: T; var l, r: TTreapNode);
+begin
+  if node = nil then
+  begin
+    l := nil;
+    r := nil;
+    Exit;
+  end;
+  if k > node.FKey then
+  begin
+    DivideLeft(node.FRight, k, node.FRight, r);
     l := node;
+  end
+  else
+  begin
+    DivideLeft(node.FLeft, k, l, node.FLeft);
+    r := node;
   end;
   UpdateSize(node);
 end;
@@ -241,7 +264,7 @@ class procedure TTreapNode.Insert(var node: TTreapNode; const k: T); inline;
   l: TTreapNode = nil;
   r: TTreapNode = nil;
 begin
-  Divide(node, k, l, r);
+  DivideRight(node, k, l, r);
   node := Meld(l, Meld(TTreapNode.Create(k), r));
 end;
 

ftreapapp.lpr

@@ -18,7 +18,7 @@
   MAX_KEY = 1000;
 
 var
-  ra: TIntTreapNode = nil;
+  ra, ln, rn: TIntTreapNode;
   ria: TImpIntTreapNode = nil;
   ta: array of longint;
   i, j: longint;
@@ -122,7 +122,42 @@
   Assert(ra = nil);
   Assert(TIntTreapNode.GetSize(ra) = 0);
 
+  for i := 0 to NODES_NUM - 1 do
+  begin
+    TIntTreapNode.Insert(ra, ta[i]);
+  end;
+  WriteLn('DivideRight test ...');
+  for i := 0 to NODES_NUM - 1 do
+  begin
+    TIntTreapNode.DivideRight(ra, ta[i], ln, rn);
+    Assert(TIntTreapNode.Contains(ln, ta[i]));
+    Assert(not TIntTreapNode.Contains(rn, ta[i]));
+    ra := TIntTreapNode.Meld(ln, rn);
+  end;
+
+  WriteLn('Check treap structure - ', TIntTreapNode.CheckStucture(ra));
+  WriteLn('Size - ', TIntTreapNode.GetSize(ra));
+
+  WriteLn('DivideLeft test ...');
+  for i := 0 to NODES_NUM - 1 do
+  begin
+    TIntTreapNode.DivideLeft(ra, ta[i], ln, rn);
+    Assert(TIntTreapNode.Contains(rn, ta[i]));
+    Assert(not TIntTreapNode.Contains(ln, ta[i]));
+    ra := TIntTreapNode.Meld(ln, rn);
+  end;
+
+  WriteLn('Check treap structure - ', TIntTreapNode.CheckStucture(ra));
+  WriteLn('Size - ', TIntTreapNode.GetSize(ra));
+
+  TIntTreapNode.DestroyTreap(ra);
+  Assert(ra = nil);
+  Assert(TIntTreapNode.GetSize(ra) = 0);
+
+  WriteLn('-----------------------');
   WriteLn('Implicit Treap test ...');
+  WriteLn('-----------------------');
+
   for i := 0 to NODES_NUM - 1 do
   begin
     TImpIntTreapNode.InsertAt(ria, 0, ta[i]);
@@ -147,9 +182,11 @@
   end;
   WriteLn('RemoveAt PASSED...');
 
-  Assert(ra = nil);
-  Assert(TIntTreapNode.GetSize(ra) = 0);
+  Assert(ria = nil);
+  Assert(TImpIntTreapNode.GetSize(ria) = 0);
   TImpIntTreapNode.DestroyTreap(ria);
-  //ReadLn();
+
+
+  ReadLn();
 
 end.