1586A - Windblume Ode - CodeForces Solution

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;

template <typename... Args>
void print(const Args&... arg) {
    ((cout << arg), ...);
}
void solve() {
    int n;
    cin >> n;
    vector<int> a(n + 1);
    int sum = 0;
    for (int i = 1; i <= n; i++)  {
        cin >> a[i];
        sum += a[i];
    }
    int ok = 0;
    for (int i = 2; i <= sum/i; i++) {
        if (sum % i == 0) ok = 1;
    }
    if (ok) {
        print(n, '\n');
        for (int i = 1; i <= n; i++) {
            print(i, " \n"[i == n]);
        }
    }else {
        print(n - 1, '\n');
        for (int i = 1; i <= n; i++) {
            if (ok || a[i] % 2 == 0) print(i, ' ');
            else if (a[i] % 2) ok = 1;
        }
        print("\n");
    }
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int t;
    cin >> t;
    while (t--) {
        solve();
    }
    return (0*0);
}