avlNode.H

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/*
                          Aleph_w
 
  Data structures & Algorithms
  version 2.0.0b
  https://github.com/lrleon/Aleph-w
 
  This file is part of Aleph-w library
 
  Copyright (c) 2002-2026 Leandro Rabindranath Leon
 
  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:
 
  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.
 
  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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*/
 
 
# ifndef AVLNODE_H
# define AVLNODE_H
 
# include <tpl_binNodeUtils.H>
 
class AvlNode_Data
{
 
  signed char diff = 0;  
 
public:
 
  AvlNode_Data() noexcept : diff(0) { /* EMPTY */ }
 
  signed char & getDiff() noexcept { return diff; }
 
  void reset() noexcept { diff = 0; }
 
};
 
# define DIFF(p) ((p)->getDiff())
 
DECLARE_BINNODE(AvlNode, 40, AvlNode_Data);
 
    template <class Node>
bool is_avl(Node* p)
{
  if (p == Node::NullPtr) 
    return true;
 
  // Balance factor must be in valid range
  if (DIFF(p) < -1 or DIFF(p) > 1)
    return false;
      
  // Compute actual heights
  const int hL = computeHeightRec(LLINK(p));
  const int hR = computeHeightRec(RLINK(p));
 
  // Verify AVL property: heights differ by at most 1
  if (const int diff = hR - hL; diff > 1 or diff < -1)
    return false;
 
  // Verify stored balance factor matches reality
  if (static_cast<int>(DIFF(p)) != hR - hL)
    return false;
 
  // Recursively check subtrees
  if (not is_avl(LLINK(p)))
    return false;
 
  return is_avl(RLINK(p));
}
 
# endif // AVLNODE_H