Four digit random number without digit repetition

Question

Is there any way you can have a 4 digit number without repetition - e.g. not 1130 but 1234? I read std::random_shuffle could do this b

Answer 1

I don't see a problem with std::random_shuffle:

#include 
#include 
#include 
#include 
#include 

int main()
{
    std::string s;    
    std::generate_n(std::back_inserter(s), 10,
        []() { static char c = '0'; return c++; });
    // s is now "0123456789"

    std::mt19937 gen(std::random_device{}());

    // if 0 can't be the first digit
    std::uniform_int_distribution dist(1, 9);
    std::swap(s[0], s[dist(gen)]);

    // shuffle the remaining range
    std::shuffle(s.begin() + 1, s.end(), gen); // non-deprecated version

    // convert only first four
    auto x = std::stoul(s.substr(0, 4));
    std::cout << x << std::endl;
}

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