public void inorder(TreeNode node)
{
if (node == null)
return;
inorder(node.left);
Console.Write(" {0} ", node.toString());
inorder(node.right);
}
private TreeNode build(string[] tokens, ref int start)
{
if(start >= tokens.Length)
return null;
bool leaf;
double val;
TreeNode node = null;
leaf = double.TryParse(tokens[start], out val);
if(leaf)
{
node = new TreeNode(leaf, '\0', val);
start++;
}
else
{
node = new TreeNode(leaf, char.Parse(tokens[start]), 0.0);
start++;
node.left = build(tokens, ref start);
node.right = build(tokens, ref start);
}
return node;
}
private double Evaluate(TreeNode node)
{
double result = 0.0;
if (node.isleaf)
result = node.val;
else
{
char op = node.op;
double left, right;
left = Evaluate(node.left);
right = Evaluate(node.right);
switch (op)
{
case '+': result = left + right;
break;
case '*': result = left * right;
break;
case '-': result = left - right;
break;
case '/':
if (right != 0)
result = left / right;
else
throw new Exception("division by zero");
break;
default: Console.WriteLine("unrecognized character: " + op);
break;
}
}
return result;
}
public void ExpressionTree(string prefixNot)
{
string[] tokens = prefixNot.Split(' ');
int start = 0;
root = build(tokens, ref start);
}
