public bool IsBst(TreeNode root)
{
// clarification question on this
if (root == null) return true;
return this.IsBST(int.MinValue, int.MaxValue, root);
}
private MaxBstResult InternalGetMaxBstInGivenTree(TreeNode root)
{
if(root == null)
{
return null;
}
MaxBstResult lResult = this.InternalGetMaxBstInGivenTree(root.Left);
MaxBstResult rResult = this.InternalGetMaxBstInGivenTree(root.Right);
// Need to handle 4 conditions on the pre order traversal..
if( lResult == null && rResult == null)
{
return new MaxBstResult{IsBST=true,TotalNodes=1,LeftVal=root.Data, RightVal=root.Data};
}
else if ( lResult != null && rResult != null)
{
if(
lResult.LeftVal <= root.Data
&& rResult.RightVal>= root.Data
&& lResult.IsBST
&& rResult.IsBST)
{
return new MaxBstResult { IsBST = true, TotalNodes = lResult.TotalNodes + rResult.TotalNodes + 1, LeftVal = lResult.LeftVal, RightVal = rResult.RightVal };
}
else
{
return new MaxBstResult{IsBST=false, TotalNodes= Math.Max(lResult.TotalNodes, rResult.TotalNodes), LeftVal =0, RightVal=0};
}
}
else if (lResult==null)
{
if( rResult.IsBST
&& root.Data <= rResult.LeftVal)
{
return new MaxBstResult{IsBST=true,TotalNodes=rResult.TotalNodes+1, LeftVal=root.Data,RightVal=rResult.RightVal};
}
else
{
return new MaxBstResult{IsBST=false,TotalNodes=rResult.TotalNodes, LeftVal=0, RightVal=0};
}
}
else
{
if (lResult.IsBST
&& root.Data >= lResult.RightVal)
{
return new MaxBstResult { IsBST = true, TotalNodes = lResult.TotalNodes + 1, LeftVal = lResult.LeftVal, RightVal = root.Data};
}
else
{
return new MaxBstResult { IsBST = false, TotalNodes = lResult.TotalNodes, LeftVal = 0, RightVal = 0 };
}
}
}
private TreeNode InternalBstInsert(int val, TreeNode root)
{
if(root == null)
{
return new TreeNode(val);
}
if(val < root.Data)
{
root.Left = this.InternalBstInsert(val, root.Left);
}
else
{
root.Right = this.InternalBstInsert(val, root.Right);
}
return root;
}
private bool IsBST(int min, int max, TreeNode root)
{
if (root == null) return true;
// Actual test for BST
if( root.Data< min || root.Data > max)
{
return false;
}
if(!this.IsBST(min, root.Data, root.Left))
{
return false;
}
if(!this.IsBST(root.Data,max, root.Right))
{
return false;
}
return true;
}
private void InternalPrint(TreeNode r)
{
}
public Tree(TreeNode root)
{
this.root = root;
}
/// <summary>
/// Find max BXT in a given tree
/// </summary>
/// <returns>Sixe of the tree(total nodes)</returns>
public int GetMaxBstInGivenTree(TreeNode root)
{
return this.InternalGetMaxBstInGivenTree(root).TotalNodes;
}