public static double EvaluatePostFixExpression(QueueUsingDoublyLinkedList <string> postfix)
{
StackUsingLinkedList <string> stack = new StackUsingLinkedList <string>();
var count = postfix.Count;
double answer = 0;
for (int i = 0; i < count; i++)
{
if (stack.Count >= 2 && postfix.Peek().Length == 1 && IsOperator(postfix.Peek()[0]) == true)
{
double x = 0;
double y = 0;
if (Double.TryParse(stack.Peek(), out x))
{
x = Convert.ToDouble(stack.Pop());
}
if (Double.TryParse(stack.Peek(), out y))
{
y = Convert.ToDouble(stack.Pop());
}
double result = Calculate(y, postfix.Dequeue()[0], x);
stack.Push(result.ToString());
}
else
{
stack.Push(postfix.Dequeue());
}
}
if (stack.Count != 0)
{
if (double.TryParse(stack.Peek(), out answer) == true)
{
answer = Convert.ToDouble(stack.Pop());
}
else
{
if (stack.Count != 1)
{
stack.Pop();
}
if (double.TryParse(stack.Peek(), out answer) == true)
{
answer = Convert.ToDouble(stack.Pop());
}
}
}
return(answer);
}
