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原始題目:

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

Note:

• Note that in some languages, such as Java, there is no unsigned integer type. In this case, the input will be given as a signed integer type. It should not affect your implementation, as the integer's internal binary representation is the same, whether it is signed or unsigned.
• In Java, the compiler represents the signed integers using 2's complement notation. Therefore, in Example 3, the input represents the signed integer. -3.

範例參考:

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.

 

Constraints:

• The input must be a binary string of length 32.

 

Follow up: If this function is called many times, how would you optimize it?

 

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解題步驟:

1.先將參數轉為二進位

2.使用迴圈讀取字串

3.當字串碰到 1 時 將num +1

4.return num 

參考程式碼:

/**
* @param {number} n - a positive integer
* @return {number}
*/
var hammingWeight = function(n) {
    
   x=n.toString(2) //轉換成二進位
   num=0
   
   for(i=0;i<x.length;i++){
       
       if(x[i]=='1'){  //讀到1字串時+1
           num+=1;
       }
   }
  
   return num
   
};

執行結果:

 

 

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