Precreation contest files

misc/hsg-hp-2025/cbai2.cpp

@@ -0,0 +1,50 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+const int max_n = 1e7;
+
+char is_prime[max_n + 1];
+void sieve() {
+  for (int i = 0; i <= max_n; i++)
+    is_prime[i] = 1;
+  is_prime[0] = 0;
+  is_prime[1] = 0;
+
+  // 2 check
+  for (int i = 4; i <= max_n; i += 2)
+    is_prime[i] = 0;
+
+  // other
+  for (int i = 3; i * i <= max_n; i += 2)
+    if (is_prime[i])
+      for (int j = i * i; j <= max_n; j += i)
+        is_prime[j] = 0;
+}
+
+int solve() {
+  int n;
+  cin >> n;
+  if (!is_prime[n])
+    return 0;
+
+  int digit_sum = 0;
+  while (n) {
+    digit_sum += n % 10;
+    n /= 10;
+  }
+  if (!is_prime[digit_sum])
+    return 0;
+  return 1;
+}
+
+int main() {
+  sieve();
+  int q;
+  cin >> q;
+  int res = 0;
+  while (q--) {
+    res += solve();
+  }
+  cout << res << "\n";
+}