private static ExpressionItemNode BuildList(char[] arr, int j)
{
ExpressionItemNode curr = null;
for (int i = 0; i <= j; i++)
{
var node = new ExpressionItemNode
{
prev = curr,
next = null,
val = char.IsDigit(arr[i]) ? (int)char.GetNumericValue(arr[i]) : (long?)null,
operand = !char.IsDigit(arr[i]) ? arr[i] : (char?)null
};
if (curr != null)
{
curr.next = node;
}
curr = node;
}
// move to head
while (curr.prev != null)
{
curr = curr.prev;
}
return(curr);
}
public ExpressionItemTransform(int offset, int length, ExpressionItemNode target, ExpressionNode transform, ExpressionNode separator)
: base(offset, length)
{
Target = target;
target.SetParent(this);
Transform = transform;
transform?.SetParent(this);
Separator = separator;
separator?.SetParent(this);
}
public ExpressionItemFunctionInvocation(int offset, int length, ExpressionItemNode target, ExpressionFunctionName methodName, ExpressionArgumentList arguments)
: base(offset, length)
{
Target = target;
target.SetParent(this);
Function = methodName;
methodName?.SetParent(this);
Arguments = arguments;
arguments?.SetParent(this);
}
private static long Evaluate(char[] arr, int j)
{
ExpressionItemNode head = BuildList(arr, j);
char[] operands = new char[] { '"', '*', '+' };
ExpressionItemNode curr = head;
for (int i = 0; i < operands.Length; i++)
{
curr = head;
while (curr != null)
{
if (curr.operand.HasValue && curr.operand == operands[i])
{
// merge the previous and the next nodes
var prev = curr.prev;
var next = curr.next;
long finalValue = 0;
if (operands[i] == '"')
{
string concated = $"{prev.val}{next.val}";
finalValue = long.Parse(concated);
}
else if (operands[i] == '*')
{
finalValue = prev.val.Value * next.val.Value;
}
else
{
finalValue = prev.val.Value + next.val.Value;
}
// delete the curr and next nodes
prev.val = finalValue;
prev.next = next.next;
if (next.next != null)
{
next.next.prev = prev;
}
// reset the curr node
curr = prev;
}
curr = curr.next;
}
}
return(head.val.Value);
}
