NumberOf1Bits(leetcode191)

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

Example 1:

Input: 11
Output: 3
Explanation: Integer 11 has binary representation 00000000000000000000000000001011 

Example 2:

Input: 128
Output: 1
Explanation: Integer 128 has binary representation 00000000000000000000000010000000

使用API

public static int hammingWeight(int n) {
     return Integer.bitCount(n);
}

API裏面寫的沒看懂，本身寫寫

//在java中不能定義unsign int 用long類型代替 測試2147483648
public static int hammingWeight2(long n) {
    int num = 0;
    while(n > 0) {
        num += n & 1;
        n = n >>> 1;
    }
    return num;
}