Question

I don’t want someone to explain how the following code works (it checks whether an int is pandigital) as I should be doing that myself. I just need help understanding line 8 specifically. I don’t know what the | is doing.

private bool isPandigital(long n) {
    int digits = 0;
    int count = 0;
    int tmp;

    while (n > 0) {
        tmp = digits;
        digits = digits | 1 << (int)((n % 10) - 1);
        if (tmp == digits) {
            return false;
        }

        count++;
        n /= 10;
    }
    return digits == (1 << count) - 1;
}

Answer 1

I know others have already explained that it’s a bitwise OR, but I’d like to give my own interpretation.

digits = digits | X will copy all the 1 bits from X into digits.

digits = digits | 1 << Y will “set” a single bit in digits – it will set the Yth bit.

So, each loop sets a bit in digits.