/// <summary>
///
/// </summary>
/// <param name="inputString">string in infix notation</param>
/// <returns></returns>
public string ReversePolishNotation(string inputString)
{
var output = string.Empty;
var stack = new Stack <char>();
for (int i = 0; i < inputString.Length; i++)
{
if (ExpressionProcessor.IsDelimeter(inputString[i]))
{
continue;
}
if (ExpressionProcessor.IsPartOfDecimalNumber(inputString[i]))
{
var value = ExpressionProcessor.GetFirstOccurrenceOfOperand(inputString, i);
output += value + " ";
i += value.Length - 1;
}
else if (ExpressionProcessor.IsOperator(inputString[i]))
{
ProcessOperator(inputString[i], stack, ref output);
}
else
{
throw new ArgumentException($"Unknown character {inputString[i]} in expression");
}
}
if (stack.Contains('('))
{
throw new ArgumentException("Closing parenthesis is missing in expression");
}
while (stack.Count != 0)
{
output += stack.Pop() + " ";
}
return(output);
}
/// <summary>
///
/// </summary>
/// <param name="inputString"></param>
/// <returns>String in reverse polish notation</returns>
public double CalculateFromReversePolishNotation(string inputString)
{
var stack = new Stack <double>();
for (int i = 0; i < inputString.Length; i++)
{
if (ExpressionProcessor.IsDelimeter(inputString[i]))
{
continue;
}
if (ExpressionProcessor.IsPartOfDecimalNumber(inputString[i]))
{
var value = ExpressionProcessor.GetFirstOccurrenceOfOperand(inputString, i);
stack.Push(double.Parse(value));
i += value.Length - 1;
}
else if (ExpressionProcessor.IsOperator(inputString[i]))
{
double operand1;
double operand2;
if (stack.Count < 2)
{
throw new ArgumentException("Something wrong with operators and operands");
}
operand2 = stack.Pop();
operand1 = stack.Pop();
var result = Calculate(operand1, operand2, inputString[i]);
stack.Push(result);
}
}
return(stack.Peek());
}