added algo for checking the number is power of four or not

madhuredra · madhuredra · commit 0e154eca3130 · 2023-09-11T20:38:00.000+05:30
diff --git a/Bit-Manipulation/IsPowerofFour.js b/Bit-Manipulation/IsPowerofFour.js
@@ -0,0 +1,24 @@
+/*
+    author: @dev-madhurendra
+
+    This script will check whether the given
+    number is a power of four or not.
+
+    A number will be power of four if and only if there is a 1 in the binary
+    of the digit and it will be at the first position
+
+    n   n-1%3==0   (n-1)bin  (n)bin
+    1   0           0           1        - 4^0
+    4   3           011         100      - 4^1
+    16  15          01111       10000    - 4^2
+    64  63          011111      1000000  - 4^3
+
+    a) There is only one bit set in the binary representation of n (or n is a power of 2)
+    b) There is only one bit unset in the n-1
+    c) And the and of n&n-1 will be 0
+    d) N-1 will be divisble by 3
+*/
+
+const IsPowerOfFour = (n) => ((n > 0) && ((n & n - 1) === 0) && (n % 3 === 1))
+
+export { IsPowerOfFour }
diff --git a/Bit-Manipulation/test/IsPowerOfFour.test.js b/Bit-Manipulation/test/IsPowerOfFour.test.js
@@ -0,0 +1,14 @@
+import { IsPowerOfFour } from '../IsPowerofFour'
+
+describe('IsPowerOfFour', () => {
+  it.each([
+    [0, false],
+    [4, true],
+    [16, true],
+    [12, false],
+    [64, true],
+    [-64, false]
+  ])('should return the number is power of four or not', (n, expected) => {
+    expect(IsPowerOfFour(n)).toBe(expected)
+  })
+})
