Added Binary Exponentiation (Recursive)

Maths/BinaryExponentiationRecursive.js

@@ -0,0 +1,31 @@
+/*
+  Modified from:
+    https://github.com/TheAlgorithms/Python/blob/master/maths/binary_exponentiation.py
+
+  Explaination:
+    https://en.wikipedia.org/wiki/Exponentiation_by_squaring
+*/
+
+const binaryExponentiation = (a, n) => {
+  // input: a: int, n: int
+  // returns: a^n: int
+  if (n === 0) {
+    return 1
+  } else if (n % 2 === 1) {
+    return binaryExponentiation(a, n - 1) * a
+  } else {
+    const b = binaryExponentiation(a, n / 2)
+    return b * b
+  }
+}
+
+const main = () => {
+  // binary_exponentiation(2, 10)
+  // > 1024
+  console.log(binaryExponentiation(2, 10))
+  // binary_exponentiation(3, 9)
+  // > 19683
+  console.log(binaryExponentiation(3, 9))
+}
+
+main()