✨ Number of 1 In Binary

Author: tangweikun

.babelrc

@@ -1,6 +1,3 @@
 {
-  "presets": [
-    "es2015",
-    "env"
-  ]
-}
+  "presets": ["es2015", "env"]
+}

src/numberOf1InBinary/README.md

@@ -0,0 +1,17 @@
+<!-- TODO: Translate Me -->
+
+# number of 1 the binary
+
+## Description
+
+* 任意给定一个 32 位无符号整数`n`,求`n`的二进制表示中 1 的个数
+
+## Example
+
+```javascript
+Input: 5
+Output: 2
+
+Input: 15
+Output: 4
+```

src/numberOf1InBinary/index.js

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+export function numberOf1InBinary(num, total = 1) {
+  if (num === 0) return 0
+  if (num === 1) return total
+  if (num % 2) {
+    return numberOf1InBinary((num - 1) / 2, total + 1)
+  }
+  return numberOf1InBinary(num / 2, total)
+}

src/numberOf1InBinary/test.js

@@ -0,0 +1,33 @@
+import { numberOf1InBinary } from '.'
+
+test('numberOf1InBinary-0', () => {
+  expect(numberOf1InBinary(0)).toBe(0)
+})
+
+test('numberOf1InBinary-1', () => {
+  expect(numberOf1InBinary(1)).toBe(1)
+})
+
+test('numberOf1InBinary-2', () => {
+  expect(numberOf1InBinary(2)).toBe(1)
+})
+
+test('numberOf1InBinary-3', () => {
+  expect(numberOf1InBinary(7)).toBe(3)
+})
+
+test('numberOf1InBinary-4', () => {
+  expect(numberOf1InBinary(17)).toBe(2)
+})
+
+test('numberOf1InBinary-5', () => {
+  expect(numberOf1InBinary(32)).toBe(1)
+})
+
+test('numberOf1InBinary-6', () => {
+  expect(numberOf1InBinary(53)).toBe(4)
+})
+
+test('numberOf1InBinary-7', () => {
+  expect(numberOf1InBinary(111)).toBe(6)
+})