Одномерный массив

#include <vector>
#include <algorithm>
#include <iostream>
#include <cstdlib>
#include <ctime>
 
int main(int argc, char* argv[])
{
    std::srand(std::time(nullptr));
    std::vector<int> data(10);
 
    for (size_t i = 0; i < data.size(); ++i)
    {
        data[i] = -280 + (std::rand() % 561);
    }
 
    unsigned int pos_num = std::count_if(data.cbegin(), data.cend(), [](const int item) {return item > 0; });
    long int sum_neg_sq = 0;
    for (size_t i = 0; i < data.size(); ++i)
    {
        if ((i % 3 == 0) && data[i] < 0)
        {
            sum_neg_sq += data[i] * data[i];
        }
    }
 
    std::cout << pos_num << std::endl;
    std::cout << sum_neg_sq << std::endl;
 
    return 0;
}

#include <iostream>
#include <cstdlib>
#include <ctime>
using namespace std;
 
int main()
{
    srand((unsigned)time(0));
    const int n=10;
    int a[n], pos=0;
    unsigned long long S=0;
 
    for (int i = 0; i < n ; i++)
    {
        a[i]=rand()%561-280;
        if(a[i]>0) pos++;
        else if (a[i]<0 && (i+1)%3==0) S+=a[i]*a[i]; 
        cout << a[i] << " ";
    }
 
    cout << "\ncount positive = " << pos << "\n"; 
    if(S) cout << "S = " << S << "\n";
    else cout << "negative elements with numbers multiple of 3 are absent\n";
 
system("pause");
return 0;
}