public double EvaluateTreeExpression(TreeChar expression)
{
//Base
if (expression == null)
{
return(0);
}
//Induction
int leaf = 0;
if (Int32.TryParse(expression.val.ToString(), out leaf))
{
return(leaf);
}
if (expression.val == '+')
{
return(EvaluateTreeExpression(expression.left) + EvaluateTreeExpression(expression.right));
}
if (expression.val == '-')
{
return(EvaluateTreeExpression(expression.left) - EvaluateTreeExpression(expression.right));
}
if (expression.val == '*')
{
return(EvaluateTreeExpression(expression.left) * EvaluateTreeExpression(expression.right));
}
if (expression.val == '/')
{
return(EvaluateTreeExpression(expression.left) / EvaluateTreeExpression(expression.right));
}
return(0);
}
private TreeChar BuildTree(string preOrder,
string inOrder,
int indexPreOrder,
int leftInOrder,
int rightInOrder,
Hashtable position)
{
//Base case
if (String.IsNullOrEmpty(preOrder) ||
String.IsNullOrEmpty(inOrder) ||
indexPreOrder >= preOrder.Length ||
leftInOrder > rightInOrder)
{
return(null);
}
//Induction
int indexInOrder = (int)position[preOrder[indexPreOrder]];
if (indexInOrder < leftInOrder || indexInOrder > rightInOrder)
{
return(BuildTree(preOrder,
inOrder,
indexPreOrder + 1,
leftInOrder,
rightInOrder,
position));
}
TreeChar tree = new TreeChar(preOrder[indexPreOrder]);
tree.left = BuildTree(preOrder,
inOrder,
indexPreOrder + 1,
leftInOrder,
indexInOrder - 1,
position);
tree.right = BuildTree(preOrder,
inOrder,
indexPreOrder + 1,
indexInOrder + 1,
rightInOrder,
position);
return(tree);
}
public TreeChar(char val)
{
this.val = val;
this.left = null;
this.right = null;
}