/// <summary>
/// Determines if the tree valid BS the specified root.
/// </summary>
/// <returns><c>true</c> if is valid BST; otherwise, <c>false</c>.</returns>
/// <param name="root">Root Node.</param>
public static bool IsValidBST(Node root)
{
if (root == null)
return(true);
if (root.Left!=null && MaxValue(root.Left) > root.Value)
return(false);
if (root.Right!=null && MinValue(root.Right) <= root.Value)
return(false);
if (!IsValidBST(root.Left) || !IsValidBST(root.Right))
return(false);
return(true);
}
public Node(int value, Node left, Node right)
{
Value = value;
Left = left;
Right = right;
}
/// <summary>
/// Finds the minimums value in the sub tree. - This is a reccursive fuction
/// </summary>
/// <returns>Minimum value in the three</returns>
/// <param name="node">Node.</param>
static int MinValue(Node node)
{
int subNodeMinValue = node.Left == null ? node.Value: MinValue (node.Left);
int minValue = node.Value > subNodeMinValue?node.Value : subNodeMinValue ;
return minValue;
}
/// <summary>
/// Finds the maximum value in the sub tree. This is a reccursive fuction
/// </summary>
/// <returns>The value.</returns>
/// <param name="node">Node.</param>
static int MaxValue(Node node)
{
int subNodeMaxValue =node.Right == null ? node.Value: MaxValue (node.Right);
int maxvalue = node.Value > subNodeMaxValue?node.Value : subNodeMaxValue ;
return maxvalue;
}