public bool IsBinaryTreeABST(BinaryTreeNode root)
{
Stack <BinaryTreeChecker> bstChecker = new Stack <BinaryTreeChecker>();
bstChecker.Push(new BinaryTreeChecker(root, int.MinValue, int.MaxValue));
while (bstChecker.Any())
{
BinaryTreeChecker rangeChecker = bstChecker.Pop();
if (rangeChecker.BinaryTree != null &&
(rangeChecker.BinaryTree.Value < rangeChecker.lowerBound || rangeChecker.BinaryTree.Value > rangeChecker.upperBound))
{
return(false);
}
if (rangeChecker.BinaryTree != null && rangeChecker.BinaryTree.Right != null)
{
BinaryTreeChecker rightRangeNode = new BinaryTreeChecker(rangeChecker.BinaryTree.Right, rangeChecker.BinaryTree.Value, rangeChecker.upperBound);
bstChecker.Push(rightRangeNode);
}
if (rangeChecker.BinaryTree != null && rangeChecker.BinaryTree.Left != null)
{
BinaryTreeChecker leftRangeNode = new BinaryTreeChecker(rangeChecker.BinaryTree.Left, rangeChecker.lowerBound, rangeChecker.BinaryTree.Value);
bstChecker.Push(leftRangeNode);
}
}
return(true);
}
public bool IsBinaryTreeABSTRecursionHelper(BinaryTreeChecker root)
{
if (root == null || root.BinaryTree == null)
{
return(true);
}
if (root != null &&
root.BinaryTree != null &&
(root.BinaryTree.Value < root.lowerBound || root.BinaryTree.Value > root.upperBound))
{
return(false);
}
bool isLeftTree = this.IsBinaryTreeABSTRecursionHelper(new BinaryTreeChecker(root.BinaryTree.Left, root.lowerBound, root.BinaryTree.Value));
bool isRightTree = this.IsBinaryTreeABSTRecursionHelper(new BinaryTreeChecker(root.BinaryTree.Right, root.BinaryTree.Value, root.lowerBound));
return(isLeftTree && isRightTree);
}