using System.Collections.Generic;
public static void Main()
string formula = "AB+FB+100";
var length = formula.Length;
List<string> variables = new List<string>();
List<char> operators = new List<char>
'+', '-', '*', '/', ')', '(', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9'
string character = string.Empty;
for (int i = 0; i < length; i++)
if (!operators.Contains(formula[i]))
if (!string.IsNullOrWhiteSpace(character))
variables.Add(character);
character = string.Empty;
if (!string.IsNullOrWhiteSpace(character))
variables.Add(character);
Console.WriteLine("Correct Behaviour Formula : AB+FB+100");
foreach (var item in variables)
variables = new List<string>();
character = string.Empty;
for (int i = 0; i < length; i++)
if (!operators.Contains(formula[i]))
if (!string.IsNullOrWhiteSpace(character))
variables.Add(character);
character = string.Empty;
if (!string.IsNullOrWhiteSpace(character))
variables.Add(character);
Console.WriteLine("InCorrect Behaviour Formula : AB1+FB1+100");
foreach (var item in variables)