PROBLEM WITH INTEGER SUM

Belli

@SeppJ sagte in PROBLEM WITH INTEGER SUM:

. Auch wir anderen merken, wenn wir verarscht werden

Spätestens bei 'cough bear' ...

bugsfinder2022

Modified code as below.

#include <iostream>

class Test {

public:
static int solve(int N)
{ int sum1 = 0;
while (N != 0)
{
sum1 += N % 10;
N /= 10;
}
return sum1;
}

static void smallestnum(int N)
{
std::cout << (N % 9 + 1)
* pow(10, (N / 9))
- 1;

}
};

int main()
{
   int N = 16; 
    Test::smallestnum(N);
    return 0;

}

Jockelx

@bugsfinder2022 Are you usually using java? Thank God, we do not have to put our free-functions in stupid and useless classes!

SeppJ

Das ist übrigens A051885, falls sich ein Leser wundert, was die Aufgabe soll.

EinNutzer0

@bugsfinder2022 If all "functions" in a class are static-defined, there is no need for such a class, especially if it contains no more than two functions.

Moreover, the class does not contain any attributes at all...

bugsfinder2022

Yes, I agree that we dont need classes nor static members here.

EinNutzer0

Ich hab mir mal die Mühe gemacht und das implementiert... Ich wäre froh, wenn noch mal jemand draufschauen könnte...

#include <iostream>
#include <vector>

class Smallest
{
public:
    long smallest_number_whose_sum_of_digits_is_n(const unsigned int n)
    {
	if(numbers.size() < n) {
	    for(unsigned int i = numbers.size(); i < n; i++) {
		smallest_number_whose_sum_of_digits_is_n(i);
	    }
	    return smallest_number_whose_sum_of_digits_is_n(n);
	}
	if(numbers.size() == n) {
	    long start = numbers.back();
	    long sum;
	    while((sum = sum_of_digits(start)) != n) {
		start++;
	    }
	    numbers.push_back(start);
	}
	return numbers[n];
    }
    long sum_of_digits(long n)
    {
	long sum = 0;
	while(n > 0) {
	    sum += n % 10;
	    n /= 10;
	}
	return sum;
    }

private:
    std::vector<long> numbers { 0 };
};

int main(int argc, char** argv)
{
    Smallest s;
    std::cout << " 5: " << s.smallest_number_whose_sum_of_digits_is_n(5) << "\n";
    std::cout << "19: " << s.smallest_number_whose_sum_of_digits_is_n(19) << "\n";
    for(int i = 10; i <= 30; i++) {
	std::cout << i << ": " << s.smallest_number_whose_sum_of_digits_is_n(i) << "\n";
    }
    return 0;
}

In der main-Methode stehen ein paar Testausgaben.

EinNutzer0

Upps, klar gab es noch ein paar Unstimmigkeiten:

#include <iostream>
#include <vector>

class Smallest
{
public:
    long smallest_number_whose_sum_of_digits_is_n(const unsigned int n)
    {
	if(numbers.size() < n) {
	    for(unsigned int i = numbers.size(); i < n; i++) {
		smallest_number_whose_sum_of_digits_is_n(i);
	    }
	}
	if(numbers.size() == n) {
	    long start = numbers.back();
	    while(sum_of_digits(++start) != n)
		;
	    numbers.push_back(start);
	}
	return numbers[n];
    }
    long sum_of_digits(long n)
    {
	long sum = 0;
	while(n > 0) {
	    sum += n % 10;
	    n /= 10;
	}
	return sum;
    }

private:
    std::vector<long> numbers { 0 };
};

int main(int argc, char** argv)
{
    Smallest s;
    std::cout << " 5: " << s.smallest_number_whose_sum_of_digits_is_n(5) << "\n";
    std::cout << "19: " << s.smallest_number_whose_sum_of_digits_is_n(19) << "\n";
    for(int i = 0; i <= 30; i++) {
	std::cout << i << ": " << s.smallest_number_whose_sum_of_digits_is_n(i) << "\n";
    }
    return 0;
}

EinNutzer0

@EinNutzer0 sagte in PROBLEM WITH INTEGER SUM:

++start

Das ist nicht besonders performant... Beispiel:

    for(int i = 0; i < std::numeric_limits<int>::max(); i++) {
	std::cout << i << ": " << s.smallest_number_whose_sum_of_digits_is_n(i) << "\n";
    }

EinNutzer0

Jetzt aber / Now for it:

#include <algorithm>
#include <iostream>
#include <limits>
#include <vector>

class Smallest
{
public:
    long smallest_number_whose_sum_of_digits_is_n(const unsigned int n)
    {
	if(n > 162) {
	    return -1;
	}
	if(numbers.size() < n) {
	    for(unsigned int i = numbers.size(); i < n; i++) {
		smallest_number_whose_sum_of_digits_is_n(i);
	    }
	}
	if(numbers.size() == n) {
	    long start = numbers.back();
	    while(sum_of_digits(start = inc_backwards(start)) != n)
		;
	    numbers.push_back(start);
	}
	return numbers[n];
    }
    long sum_of_digits(long n)
    {
	long sum = 0;
	while(n > 0) {
	    sum += n % 10;
	    n /= 10;
	}
	return sum;
    }
    long inc_backwards(long n)
    {
	std::string s = std::to_string(n);
	std::reverse(s.begin(), s.end());
	if(s.back() == '9') {
	    s.push_back('0');
	}
	s = std::to_string(std::stol(s) + 1);
	std::reverse(s.begin(), s.end());
	return std::stol(s);
    }

private:
    std::vector<long> numbers { 0 };
};

int main(int argc, char** argv)
{
    Smallest s;
    for(int i = 0; i <= 200; i++) {
	std::cout << i << ": " << s.smallest_number_whose_sum_of_digits_is_n(i) << "\n";
    }
    return 0;
}

Leon0402

@EinNutzer0 Warum nicht die Formel?

#include <iostream>
#include <cmath>

int main(int argc, char** argv)
{
    for(int i = 0; i <= 50; i++) {
        std::cout << i << ": " << (i%9 + 1) * std::pow(10, i / 9) - 1 << "\n";
    }
}

EinNutzer0

@Leon0402 Das sieht auch gut aus, ich dachte zunächst, es sollte algorithmisch gelöst werden.