A - Windblume Ode

https://codeforces.com/contest/1586/submission/132232729

CodeForces/1586/A/A.cpp

@@ -0,0 +1,53 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+int t, n, a[105], sum, p1, p2;
+bool is_prime[20005];
+
+void Eratosthenes(int n) {
+    for (int i = 0; i <= n; i++) is_prime[i] = true;
+    is_prime[0] = is_prime[1] = false;
+    for (int i = 2; i <= n; i++) {
+        if (is_prime[i]) {
+            if (i * i <= n) {
+                for (int j = i * i; j <= n; j += i) {
+                    is_prime[j] = false;
+                }
+            }
+        }
+    }
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin >> t;
+    Eratosthenes(20000);
+    while (t--) {
+        sum = 0;
+        p1 = p2 = -1;
+        cin >> n;
+        for (int i = 1; i <= n; i++) {
+            cin >> a[i];
+            if (a[i] == 1) p1 = i;
+            if (a[i] % 2) p2 = i;
+            sum += a[i];
+        }
+        cout << n - is_prime[sum] << endl;
+        if (!is_prime[sum]) {
+            for (int i = 1; i <= n; i++) {
+                cout << i << ' ';
+            }
+        } else if (p1 != -1) {
+            for (int i = 1; i <= n; i++) {
+                if (i != p1) cout << i << ' ';
+            }
+        } else {
+            for (int i = 1; i <= n; i++) {
+                if (i != p2) cout << i << ' ';
+            }
+        }
+        cout << endl;
+    }
+    return 0;
+}