private string ShuntingYard(string input)
{
LinkedListStack <char> operators = new LinkedListStack <char>();
Queue <char> output = new LinkedListQueue <char>();
foreach (var i in input)
{
if (Char.IsNumber(i))
{
output.Enqueue(i);
}
if (IsOperator(i))
{
while (!operators.IsEmpty() && OperatorPrecedence(operators.Peek()) >= OperatorPrecedence(i))
{
output.Enqueue(operators.Pop());
}
operators.Push(i);
}
if (i == '(')
{
operators.Push(i);
}
if (i == ')')
{
while (operators.Peek() != '(')
{
output.Enqueue(operators.Pop());
}
operators.Pop();
}
}
while (!operators.IsEmpty())
{
output.Enqueue(operators.Pop());
}
return(new string(output.ToArray()));
}