Read an Integer as int and check for repeating digits

Question

I have to enter a number(int) from the console and to check for a repeating digits in this number, but I must not use an array, and here I find it difficult.

Can anyone help me with a code?

Answer 1

You could use an integer to store which digits were entered:

#include <cstdint>
#include <iostream>

class DigitContainer {
public:
    bool contains(std::uint8_t digit) {
        return container & 1 << digit;
    }

    void set(std::uint8_t digit) {
        container |= 1 << digit;
    }
private:
    std::uint16_t container{};
};

int main() {
    DigitContainer keyPress;
    DigitContainer printed;
    std::uint64_t number;
    std::cin >> number;
    std::cout << "Repeated:\n";
    for (; number; number /= 10) {
        std::uint8_t digit = number % 10;
        if (keyPress.contains(digit)) {
            if (!printed.contains(digit)) {
                std::cout << static_cast<int>(digit) << "\n";
                printed.set(digit);
            }
        } else {
            keyPress.set(digit);
        }
    }
}