algorithm: Log2 using bitwise operations (#1132)

acarlson99 · web-flow · commit 78f023fdd174 · 2022-10-09T17:36:23.000+05:30
diff --git a/Bit-Manipulation/LogTwo.js b/Bit-Manipulation/LogTwo.js
@@ -0,0 +1,14 @@
+/**
+ * https://handwiki.org/wiki/Binary_logarithm
+ * Approximate log2 using only bitwise operators
+ * @param {number} n
+ * @returns {number} Log2 approximation equal to floor(log2(n))
+ */
+export const logTwo = (n) => {
+  let result = 0
+  while (n >> 1) {
+    n >>= 1
+    result++
+  }
+  return result
+}
diff --git a/Bit-Manipulation/test/LogTwo.test.js b/Bit-Manipulation/test/LogTwo.test.js
@@ -0,0 +1,7 @@
+import { logTwo } from '../LogTwo'
+
+for (let i = 1; i < 100; i++) {
+  test('log2(' + i + ')', () => {
+    expect(logTwo(i)).toBe(Math.floor(Math.log2(i)))
+  })
+}
