Bonus

#include <iostream>
using namespace std;
struct spair
{
    int a, b, sum;
    inline bool operator<(const spair& o) const
    {
        if (sum < o.sum) { return true; }
        if (sum > o.sum) { return false; }
        if (a < o.a) { return true; }
        if (a > o.a) { return false; }
        return b < o.b;
    }
    inline bool operator>(const spair& o) const { return !(operator<(o)); }
};
template<typename T>
void fix_heap(T a[], int i, int n)
{
    int j = 2 * i + 1;
    while (j < n)
    {
        if (j + 1 < n && a[j + 1] > a[j]) { j++; }
        if (a[j] > a[i])
        {
            swap(a[j], a[i]);
            i = j;
            j = 2 * i + 1;
        }
        else { break; }
    }
}
template<typename T>
void construct_heap(T a[], int n)
{
    for (int i = (n - 2) / 2; i >= 0; i--) { fix_heap(a, i, n); }
}
template<typename T>
void heap_sort(T a[], int n)
{
    construct_heap(a, n);
    for (int i = n - 1; i > 0; i--)
    {
        swap(a[0], a[i]);
        fix_heap(a, 0, i);
    }
}
int find(spair a[], int n, int sum)
{
    int l = 0, r = n - 1, m;
    while (l <= r)
    {
        m = (l + r) / 2;
        if (a[m].sum < sum) {l = m + 1; }
        else if (a[m].sum > sum) { r = m - 1; }
        else { return m; }
    }
    return -1;
}
void solve(int a[], int as, int b[], int bs, int c[], int cs)
{
    spair* fs = new spair[bs * cs];
    int fsi = 0;
    for (int ai = 0; ai < as; ai++)
    {
        for (int bi = 0; bi < bs; bi++)
        {
            fs[fsi].a = a[ai];
            fs[fsi].b = b[bi];
            fs[fsi].sum = a[ai] + b[bi];
            fsi++;
        }
    }
    heap_sort(fs, fsi);
    int idx = -1,ci = 0;
    for (; ci < cs && idx != -1; ci++)
    {
        idx = find(fs, fsi, -c[ci]);
    }
    if (idx != -1)
    {
        ci--;
        cout << "First number: " << fs[idx].a
            << "\nSecond number: " << fs[idx].b
            << "\nThird number: " << c[ci] << endl;
    }
    else
    {
        cout << "Didn't find any valid triple!" << endl;
    }
    delete[] fs;
}
int main()
{
    const int SZ = 5;
    int a[SZ]{ 0,2,0,0,5 }, b[SZ]{ -6,8,0,7,6 }, c[SZ]{2,0,5,7,8};
    solve(a, SZ, b, SZ, c, SZ);
}