Add 19699.cpp

19xxx/19699.cpp

@@ -0,0 +1,56 @@
+#include <iostream>
+#include <set>
+#include <vector>
+using namespace std;
+
+int n, m;
+vector<int> h;
+vector<bool> prime;
+set<int> ans;
+
+vector<bool> sieve(int n) {
+  vector<bool> prime(n+1, true);
+  prime[0] = prime[1] = false;
+  for (int i=4; i<=n; i+=2) {
+    prime[i] = false;
+  }
+
+  for (int i=3; i*i<=n; i+=2) {
+    if (!prime[i]) continue;
+    for (int j=i*i; j<=n; j+=i*2) {
+      prime[j] = false;
+    }
+  }
+  return prime;
+}
+
+void backtrack(int cnt, int idx, int sum) {
+  if (cnt == m) {
+    if (prime[sum]) ans.insert(sum);
+    return;
+  }
+
+  for (int i=idx; i<n-m+cnt+1; i++) {
+    backtrack(cnt+1, i+1, sum+h[i]);
+  }
+}
+
+void solve(void) {
+  cin >> n >> m;
+  h.resize(n);
+  for (int i=0; i<n; i++) cin >> h[i];
+
+  backtrack(0, 0, 0);
+
+  if (ans.empty()) ans.insert(-1);
+  for (int a : ans) cout << a << " ";
+}
+
+int main(void) {
+  ios::sync_with_stdio(false);
+  cin.tie(nullptr);
+
+  prime = sieve(9000);
+  solve();
+  return 0;
+}