chore: import upstream snapshot with attribution

math/primes_up_to_billion.cpp

@@ -0,0 +1,36 @@
+/**
+ * @file
+ * @brief Compute prime numbers upto 1 billion
+ * @see prime_numbers.cpp sieve_of_eratosthenes.cpp
+ */
+#include <cstring>
+#include <iostream>
+
+/** array to store the primes */
+char prime[100000000];
+
+/** Perform Sieve algorithm */
+void Sieve(int64_t n) {
+    memset(prime, '1', sizeof(prime));  // intitize '1' to every index
+    prime[0] = '0';                     // 0 is not prime
+    prime[1] = '0';                     // 1 is not prime
+    for (int64_t p = 2; p * p <= n; p++) {
+        if (prime[p] == '1') {
+            for (int64_t i = p * p; i <= n; i += p)
+                prime[i] = '0';  // set all multiples of p to false
+        }
+    }
+}
+
+/** Main function */
+int main() {
+    Sieve(100000000);
+    int64_t n;
+    std::cin >> n;  // 10006187
+    if (prime[n] == '1')
+        std::cout << "YES\n";
+    else
+        std::cout << "NO\n";
+
+    return 0;
+}