Question

int countConsonant(string str, int consonant)
{
    int length = str.length();
     consonant = 0;

        for (int i = 0; i < length; i++)
        {
            if(str[i] == 'b'&& str[i] == 'c' && str[i] == 'd'&& str[i] == 'f'
                && str[i] == 'g'&& str[i] == 'h'&& str[i] == 'j' && str[i] == 'k'&& str[i] == 'l'&& str[i] == 'm'
                && str[i] == 'n'&& str[i] == 'p'&& str[i] == 'q'&& str[i] == 'r'&& str[i] == 's'&& str[i] == 't'
                && str[i] == 'v'&& str[i] == 'w'&& str[i] == 'x'&& str[i] == 'y'&& str[i] == 'z')

                consonant = consonant + 1;
        }
        return consonant;
}

Answer 1

You were close, but should check with logical-or ||, not logical-and && (str[i] simply can’t be equal to two different things).

The C++03 Standard allows you to use the keywords and and or – and not, xor etc – instead of these cryptic (for new programmers) symbols, but this hasn’t caught on widely – perhaps because Microsoft’s compiler doesn’t default to being Standard-compliant in this regard – presumably to avoid breaking existing client code that has variables, functions, types etc. with these names. So, for portability and simplicity, many libraries and textbooks avoid these keywords too.

Another approach that might be a little more concise is to use isalpha() from <cctype> then check it’s not a vowel. Faster approaches tend to use arrays from character value to bool, but beware indexing outside the array due to signed character values or >=128 bit non-ASCII values. If there’s also uppercase/lowercase to consider – you may want to use tolower() on your character before testing it (i.e. char c = tolower(str[i])); if (c == '...).

Other notes: your function should:

• accept its std::string argument by const reference (i.e. const std::string& str) to avoid unnecessary and time-consuming copying of the value from the calling context into a separate variable local to this function. The copying doesn’t do any real functional harm, but it’s unnecessary.
• make consonant a local variable rather than a function parameter, as any inputted value is immediately clobbered with 0, and the result it returned by the function rather than written into consonant (which would be impossible as it is passed by value rather than passed by pointer/reference).