191. Number of 1 Bits

Author: swiftwind0405

README.md

@@ -255,7 +255,7 @@
 |198|[House Robber](https://leetcode.com/problems/house-robber/)| [js](./algorithms/houseRobber/Solution.js) |Easy|
 |197|[Rising Temperature](https://leetcode.com/problems/rising-temperature/)| [Mysql](./algorithms/risingTemperature/Solution.sql) |Easy| 
 |196|[Delete Duplicate Emails](https://leetcode.com/problems/delete-duplicate-emails/)| [Mysql](./algorithms/deleteDuplicateEmails/Solution.sql) |Easy| 
-|191|[Number of 1 Bits](https://leetcode.com/problems/number-of-1-bits/)| [java](./algorithms/numberof1bits/Solution.java) |Easy|
+|191|[Number of 1 Bits](https://leetcode.com/problems/number-of-1-bits/)| [java](./algorithms/numberof1bits/Solution.java), [js](./algorithms/numberof1bits/Solution.js) |Easy|
 |190|[Reverse Bits](https://leetcode.com/problems/reverse-bits/)| |Easy|
 |189|[Rotate Array](https://leetcode.com/problems/rotate-array/)| |Easy|
 |188|[Best Time to Buy and Sell Stock IV](https://leetcode.com/problems/best-time-to-buy-and-sell-stock-iv/)| |Hard|

algorithms/numberof1bits/Solution.js

@@ -0,0 +1,17 @@
+/**
+ * @param {number} n - a positive integer
+ * @return {number}
+ */
+var hammingWeight = function(n) {
+    let result = 0
+    // 二进制第一位是符号位，所以指需要循环后面31位
+    for(let i = 0; i < 32; i++) {
+        // (1 << i) 表示将数字1向左移动 i 位得到的值，即将二进制数1左移 i 位，得到一个只有第i位为1的二进制数
+        // 运算符 & 用于将 n 的二进制表示和 (1 << i) 的二进制表示进行按位与运算。这将返回一个新的数字，其中只有当 n 的二进制表示中的第 i 位为1时，结果中的第 i 位才为1，否则为0
+        // (n & (1 << i)) 这个表示 n 的二进制表示中的第 i 位是 0 还是 1
+        if ((n & (1 << i)) !== 0) {
+            result++
+        }
+    }
+    return result
+};