private List <PolishNotationToken> ReversePolishNotation(string s)
{
var result = new List <PolishNotationToken>();
var operatorsStack = new Stack <PolishNotationTokenOperator>();
int i = 0;
while (i < s.Length)
{
if (IsDigit(s[i]))
{
int d = 0;
while (i < s.Length && IsDigit(s[i]))
{
d = d * 10 + CharToInt(s[i]);
i++;
}
result.Add(new PolishNotationTokenNumber(d));
}
else if (s[i] == ' ')
{
while (i < s.Length && s[i] == ' ')
{
i++;
}
}
else if (PolishNotationTokenOperator.IsOperator(s[i]))
{
var newOperator = new PolishNotationTokenOperator(s[i]);
while (operatorsStack.Count != 0 &&
operatorsStack.Peek().OperatorPrecedence >= newOperator.OperatorPrecedence)
{
result.Add(operatorsStack.Pop());
}
operatorsStack.Push(newOperator);
i++;
}
}
while (operatorsStack.Count != 0)
{
result.Add(operatorsStack.Pop());
}
return(result);
}
private int PerformOperation(int left, int right, PolishNotationTokenOperator op)
{
switch (op.Operator)
{
case '+':
return(left + right);
case '*':
return(left * right);
case '-':
return(left - right);
case '/':
return(left / right);
default:
throw new NotImplementedException();
}
}
