sieve of eratosthenes

Maths/SieveofEratosthenes/SieveofEratosthenes.cpp

@@ -0,0 +1,35 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+vector<bool> is_prime;
+
+void init_sieve() {
+    int n = 1000000;
+    is_prime.assign(n+1, true);
+
+    is_prime[0] = is_prime[1] = false;
+    for (int i = 2; i * i <= n; i++) {
+    if (is_prime[i]) {
+        for (int j = i * i; j <= n; j += i)
+            is_prime[j] = false;
+    }
+}
+}
+
+int main() {
+    init_sieve();
+
+    int Q;
+    cin >> Q;
+
+    while (Q--) {
+        int x;
+        cin >> x;
+
+        if (is_prime[x]) {
+            cout << x << " is a prime number" << endl;
+        } else {
+            cout << x << " is not a prime number" << endl;
+        }
+    }
+}