Leetcode：191. Number of 1 Bits（返回一个数字对应二进制中1的个数）

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

For example, the 32-bit integer ’11’ has binary representation 00000000000000000000000000001011, so the function should return 3.

简单解法，效率不高.

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

利用&来计算

  public int hammingWeight(int n) {
       int count = 0;
        while(n!=0) {
            count = count + (n & 1);// n&1 求最低位是0还是1
            n= n>>>1; //n = n/2
        }
        return count;
    }