public decimal EvaluatePostfix(string input)
{
LinkedListStack <decimal> stack = new LinkedListStack <decimal>();
foreach (var i in input)
{
if (IsOperator(i))
{
decimal result;
var right = decimal.Parse(stack.Pop().ToString());
var left = decimal.Parse(stack.Pop().ToString());
switch (i)
{
case '+':
result = left + right;
break;
case '-':
result = left - right;
break;
case '*':
result = left * right;
break;
case '/':
result = left / right;
break;
default:
result = 0;
break;
}
stack.Push(result);
}
else
{
stack.Push(decimal.Parse(i.ToString()));
}
}
return(stack.First());
}
private string InsertParens(string input)
{
LinkedListStack <string> stack = new LinkedListStack <string>();
foreach (var i in input)
{
if (i.Equals(')'))
{
string expression = ")";
for (var j = 0; j < 3; j++)
{
expression = stack.Pop() + expression;
}
expression = "(" + expression;
stack.Push(expression);
}
else
{
stack.Push(i.ToString());
}
}
return(stack.First());
}
