LeetCode Js-191. Number of 1 Bits

    AllenLi
    LeetCode Js-String

    Write a function that takes an unsigned integer and returns the number of ‘1’ bits it has (also known as the Hamming weight).

    編寫一個函式，且可從一個沒有符號的數列中，回傳符合 '1' 的數量。

    Example 1:

    Input: n = 00000000000000000000000000001011
Output: 3
Explanation: The input binary string 00000000000000000000000000001011 
             has a total of three '1' bits.

    Example 2:

    Input: n = 00000000000000000000000010000000
Output: 1
Explanation: The input binary string 00000000000000000000000010000000 
             has a total of one '1' bit.

    Example 3:

    Input: n = 11111111111111111111111111111101
Output: 31
Explanation: The input binary string 11111111111111111111111111111101 
             has a total of thirty one '1' bits.

    Solution:
    1. 宣告 count 次數為 0。
    2. 宣告 nums 為 n.toString 二進制的字串，且將陣列中的每個數值分割為單一元素。

    Ex. Input = 3
toString(2) = 00000000000000000000000000001011
toString(2).split("") = 
[
  '0', '0', '0', '0', '0', '0',
  '0', '0', '0', '0', '0', '0',
  '0', '0', '0', '0', '0', '0',
  '0', '0', '0', '0', '0', '0',
  '0', '0', '0', '0', '1', '0',
  '1', '1'
]

    3. 運用「for in」將每個元素皆除以2，如果剩餘1，則 count++。
    4. 回傳 count 次數。

    Code:

    var hammingWeight = function(n) {
  let count = 0
  let nums = n.toString(2).split("");

  for (let num in nums) {
    if (nums[num] % 2 === 1) {
      count ++
    }
  }
  return count
};

    FlowChart:
    Example 1

    Input: n = 00000000000000000000000000001011
                                       1 23 
Output count = 3

    Example 2

    Input: n = 00000000000000000000000010000000
                                   1
Output count = 1

    Example 3

    Input: n = 11111111111111111111111111111101
           1---------------------------->31
Output count = 31

    .toString(2)：

    const x = 6;
console.log(x.toString(2));       // displays '110'

    .split()：

    const str = 'The quick brown fox jumps over the lazy dog.';

const words = str.split(' ');
console.log(words[3]);
// expected output: "fox"

const chars = str.split('');
console.log(chars[8]);
// expected output: "k"

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