백준 1929 c++

#include <iostream>
#include <vector>

using namespace std;

int input(int lower, int upper);
void eratosthenes(int A, int B, vector <int>& vi);
void find_prime(int A, int B, vector <int>& vi);
void print_result(vector <int>& vi);

int main(void)
{
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	cout.tie(NULL);

	int M, N;
	vector <int> prime;

	M = input(1, 1000000);
	N = input(M, 1000000);
	eratosthenes(M, N, prime);
	//find_prime(M, N, prime);
	print_result(prime);

	return 0;
}

int input(int lower, int upper)
{
	//cout << "input" << endl;
	int A;

	while (1)
	{
		cin >> A;
		if (A >= lower && A <= upper)
		{
			break;
		}
		else
		{
			;
		}
	}

	return A;
}

void eratosthenes(int A, int B, vector <int> &vi)
{
	//cout << "eratosthenes" << endl;
	bool* eratostenes;
	int i, j;

	eratostenes = new bool[B + 1] {false};

	for (i = 2; i <= B; i++)
	{
		eratostenes[i] = true;
	}
	for (i = 2; i * i <= B; i++)
	{
		if (eratostenes[i] == true)
		{
			for (j = i * i; j <= B; j = j + i)
			{
				eratostenes[j] = false;
			}
		}
	}
	for (i = 1; i <= B; i++)
	{
		if (eratostenes[i] == true && i >= A && i <= B)
		{
			vi.push_back(i);
		}
		else
		{
			;
		}
	}

	delete[] eratostenes;

	return;
}

void find_prime(int A, int B, vector <int> &vi)
{
	//cout << "find_prime" << endl;
	int i, j;

	for (i = A; i <= B; i++)
	{
		for (j = 2; j * j <= i; j++)
		{
			if (i % j == 0)
			{
				break;
			}
			else
			{
				;
			}
		}
		if (j * j > i && i != 1)
		{
			vi.push_back(i);
		}
		else
		{
			;
		}
	}

	return;
}

void print_result(vector <int>& vi)
{
	//cout << "print_result" << endl;
	int i;

	for (i = 0; i < vi.size(); i++)
	{
		cout << vi[i] << "\n";
	}

	return;
}