init

SieveOfEratosthenes.hpp

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+#include <array>
+#include <array>
+#include <cmath>
+
+using namespace std;
+
+template <typename U, typename F>
+constexpr size_t c_div(U a, F b)
+{
+  return static_cast<U>(a / b + 0.5);
+};
+
+template <size_t N>
+class Primes
+{
+public:
+  constexpr Primes()
+  {
+    for (size_t i = 0; i < N; i++)
+      b[i] = 1;
+
+    for (size_t i = 2; i <= N; i++)
+      if (b[i-1])
+        for (size_t j = 2 * i; j <= N; j += i)
+          b[j-1] = 0;
+
+    for (size_t i = 1; i < N; i++)
+      if (b[i])
+        arr[n++] = i+1;
+  };
+
+  size_t n;
+  array<bool, N> b;
+  array<size_t, N> arr;
+};

main.cpp

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+#include <fstream>
+#include <iostream>
+#include <array>
+#include <array>
+
+// #include "SieveOfEratosthenes.hpp"
+
+using namespace std;
+
+template <size_t N>
+class Primes
+{
+public:
+  constexpr Primes()
+  {
+    bool b[N]{0};
+
+    for (size_t i = 2; i <= N; i++)
+      if (!b[i-1])
+        for (size_t j = 2 * i; j <= N; j += i)
+          b[j-1] = 1;
+
+    for (size_t i = 1; i < N; i++)
+      if (!b[i])
+        arr[n++] = i+1;
+  };
+
+  size_t n = 0;
+  array<size_t, N> arr{};
+};
+
+int main () {
+  constexpr Primes< 262144U > primes;
+
+  ofstream out("out.txt");
+
+  for (size_t i = 0; i < primes.n; i++)
+    out << primes.arr[i] << endl;
+
+  out.close();
+}