Merge pull request codewithdev#106 from jineshparakh/master

Added Rabin Miller Algorithm

Author: codewithdev

09- Number Theory/rabinMiller.cpp

@@ -0,0 +1,57 @@
+#include<bits/stdc++.h>
+using namespace std;
+#define ll long long
+#define ld long double
+#define rep(i,a,b) for(ll i=a;i<b;i++)
+#define repp(i,a,b) for(ll i=a;i<=b;i++)
+#define rrep(i,a,b) for(ll i=a;i>=b;i--)
+#define endl "\n"
+
+ll k = 6;
+ll exp(ll x, ll y, ll p) {
+    ll res = 1;
+    while (y) {
+        if (y % 2)
+            res = (res * x % p) % p;
+        x = (x * x) % p;
+        y /= 2;
+    }
+    return res;
+}
+
+bool miller(ll d, ll n) {
+    ll a = 2 + rand() % (n - 4);
+    ll x = exp(a, d, n);
+    if (x == 1 || x == n - 1)
+        return true;
+    while (d != n - 1) {
+        x = (x * x) % n;
+        d = d * 2;
+        if (x == 1) return false;
+        if (x == n - 1) return true;
+    }
+    return false;
+}
+bool isPrime(ll n) {
+    if (n < 2 || n == 4) return false;
+    if (n <= 3) return true;
+    ll d = n - 1;
+    while (!(d & 1)) {
+        d /= 2;
+    }
+    rep(i, 0, k) {
+        if (!miller(d, n))
+            return false;
+    }
+    return true;
+}
+int main() {
+
+    ll n; cin >> n;
+    cout << isPrime(n);
+    return 0;
+    
+}
+
+
+