Question

my program should print a message on the screen if the formula that the user entered is good for the terms(you can only use digits and letters, u can’t start with ‘(‘ and like mathematical formula, for each open bracket, has to be a suitable(and in the right place) close bracket.

here some formulas that the program should accepts and prints:

True-

• a(aa(a)aaa(aa(a)aa)aa)aaaaa
• a(((())))

here some formulas that the program should not accepts and prints:

False-

• ()()()
• )()()(

but the program always prints False
thanks for helping
Heres the code:EDIT

    bool IsNumeric(char character)
    {
        return "0123456789".Contains(character);
        // or return Char.IsNumber(character);
    }

    bool IsLetter(char character)
    {
        return "ABCDEFGHIJKLMNOPQRSTUVWXWZabcdefghigjklmnopqrstuvwxyz".Contains(character);

    }

    bool IsRecognized(char character)
    {
        return IsBracket(character) | IsNumeric(character) | IsLetter(character);
    }
    public bool IsValidInput(string input)
    {
        if (String.IsNullOrEmpty(input) || IsBracket(input[0]))
        {
            return false;
        }
        var bracketsCounter = 0;
        for (var i = 0; i < input.Length; i++)
        {
            var character = input[i];
            if (!IsRecognized(character))
            {
                return false;
            }
            if (IsBracket(character))
            {
                if (character == '(')
                    bracketsCounter++;
                if (character == ')')
                    bracketsCounter--;
            }
        }


        if (bracketsCounter > 0)
        {
            return false;
        }

        return bracketsCounter==0;
    }
}
}

Answer 1

Is debugging this hard really? This condition:

((!IsNumeric(st[i])) && (st[i] != '(') && (st[i] != ')')&&((st[i]<'a')||(st[i]>'z')||(st[i]<'A')||(st[i]>'Z')))
    return false;

is obviously wrong. It returns false for a every time. You don’t take into consideration that a is greater than Z.

EDIT:

so how can i make it easier to read? that the only way i figured. do u
have other solution for this problem?

As for that condition block – use smaller methods / functions, for example.

bool IsBracket(char character)
{
    return (character == '(' | character == ')');
}

bool IsNumeric(char character)
{
    return "0123456789".Contains(character);
    // or return Char.IsNumber(character);
}

bool IsLetter(char character)
{
    // see why this is NOT prone to fail just because 'a' is greater than 'Z' in C#?
    return (character >= 'a' & character <= 'z') |
        (character >= 'A' & character <= 'Z');

    // or return Regex.IsMatch(character.ToString(), "[a-zA-Z]", RegexOptions.None);
    // or return Char.IsLetter(character);
}

// now you can implement:
bool IsRecognized(char character)
{
    return IsBracket(character) | IsNumeric(character) | IsLetter(character);
}

and then in your big method you could just safely use:

if (!IsRecognized(st[i]))
    return false;

It may look like an overkill for such a trivial example, but it’s a better approach in principle, and certainly more readable.

And after that, you could reduce your code to something along the lines of:

    bool IsInputValid(string input)
    {
        if (String.IsNullOrEmpty(input) || IsBracket(input[0]))
        {
            return false;
        }
        var bracketsCounter = 0;
        for (var i = 0; i < input.Length; i++)
        {
            var character = input[i];
            if (!IsRecognized(character))
            {
                return false;
            }
            if (IsBracket(character)) // redundant?
            {
                if (character == '(') // then what?
                if (character == ')') // then what?
            }
            if (bracketsCounter < what?)
            {
                what?
            }
        }
        return bracketsCounter == what?;
    }

(dasblinkenlight‘s algorithm)

EDIT 10th April

You got it wrong.

    bool IsNumeric(char character)
    {
        return "0123456789".Contains(character);
        // or return Char.IsNumber(character);
    }

    bool IsLetter(char character)
    {
        return "ABCDEFGHIJKLMNOPQRSTUVWXWZabcdefghigjklmnopqrstuvwxyz".Contains(character);

    }

    bool IsRecognized(char character)
    {
        return IsBracket(character) | IsNumeric(character) | IsLetter(character);
    }
    public bool IsValidInput(string input)
    {
        if (String.IsNullOrEmpty(input) || IsBracket(input[0]))
        {
            return false;
        }
        var bracketsCounter = 0;
        for (var i = 0; i < input.Length; i++)
        {
            var character = input[i];
            if (!IsRecognized(character))
            {
                return false;
            }
            if (IsBracket(character))
            {
                if (character == '(')
                    bracketsCounter++;
                if (character == ')')
                    bracketsCounter--;
            }
            // !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
            if (bracketsCounter < 0) // NOT "> 0", and HERE - INSIDE the for loop
            {
                return false;
            }
            // !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
        }

        return bracketsCounter==0;
    }
}
}

By the way, you also made a mistake in your IsLetter method:
…UVWXWZ? Should be UVWXYZ