Added Miller Rabin for 64-bit integers

Author: Amal-Verma

Maths/MillerRabin.js

@@ -0,0 +1,70 @@
+/**
+* @function millerRabin
+* @description Check if number is prime or not (accurate for 64-bit integers)
+* @param {Integer} n
+* @returns {Boolean} true if prime, false otherwise
+* @url https://en.wikipedia.org/wiki/Miller%E2%80%93Rabin_primality_test
+* note: Here we are using BigInt to handle large numbers
+**/
+
+// Modular Binary Exponentiation (Iterative)
+const binaryExponentiation = (base, exp, mod) => {
+  base = BigInt(base)
+  exp = BigInt(exp)
+  mod = BigInt(mod)
+
+  let result = BigInt(1)
+  base %= mod
+  while(exp){
+    if (exp & 1n){
+      result = (result * base) % mod
+    }
+    base = (base * base) % mod
+    exp = exp >> 1n
+  }
+  return result
+}
+
+// Check if number is composite
+const checkComposite = (n, a, d, s) => {
+  let x = binaryExponentiation(a, d, n)
+  if (x == 1n || x == (n - 1n)){
+    return false
+  }
+
+  for (let r = 1; r < s; r++){
+    x = (x * x) % n
+    if (x == n - 1n){
+      return false
+    }
+  }
+  return true
+}
+
+// Miller Rabin Primality Test
+export const millerRabin = (n) => {
+  n = BigInt(n)
+
+  if (n < 2){
+    return false
+  }
+
+  let s = 0n
+  let d = n - 1n
+  while((d & 1n) == 0){
+    d = d >> 1n
+    s++;
+  }
+
+  // Only first 12 primes are needed to be check to find primality of any 64-bit integer
+  let prime = [2n, 3n, 5n, 7n, 11n, 13n, 17n, 19n, 23n, 29n, 31n, 37n]
+  for(let a of prime){
+    if (n == a){
+      return true
+    }
+    if (checkComposite(n, a, d, s)){
+      return false
+    }
+  }
+  return true;
+}