Miller-Rabin素数测试

Miller-Rabin.cpp

@@ -0,0 +1,56 @@
+#include <cstdio>
+#include <cstdlib>
+
+#define LOWBIT(x) ((x) & (-(x)))
+
+#define COMPOSITE 0
+#define PRIME 1
+
+typedef long long ll;
+
+using namespace std;
+
+ll qpow(ll x, int y, int p)
+{
+	if (y == 0) return 1;
+	ll h = qpow(x * x % p, y >> 1, p);
+	if ((y & 1) == 0) return h;
+	else return h * x % p;
+}
+
+bool witness(int a, int n)
+{
+	int t = LOWBIT(n - 1);
+	int u = n / t;
+	ll x = qpow(a, u, n);
+	for (int i = 1; i < t; i <<= 1)
+	{
+		ll r = x * x % (ll)n;
+		if (r == 1 && x != 1 && x != n - 1) return true;
+		x = r;
+	}
+	if (x != 1) return true;
+	return false;
+}
+
+bool Miller_Rabin(int n, int s)
+{
+	if (n == 2) return PRIME;
+	if ((n & 1) == 0) return COMPOSITE;
+	while (s--)
+	{
+		if (witness(rand() % (n - 2) + 2, n) == true) return COMPOSITE;
+	}
+	return PRIME;
+}
+
+int main()
+{
+	int n;
+	while (true)
+	{
+		scanf("%d", &n);
+		printf("%s\n", Miller_Rabin(n, 10) == COMPOSITE ? "COMPOSITE" : "PRIME");
+	}
+	return 0;
+}