191. 位 1 的个数

00000000000000000000000000001011 中，共有三位为 '1'。

HAMMING-WEIGHT(n)
    r = 0
    while n != 0
        n &= n - 1
        r += 1
    r

[0, 1, 0, 1] // 5
[0, 1, 0, 0] // 5 - 1 = 4
[0, 1, 0, 0] // 5 & 4 = 4

[0, 1, 0, 0] // 4
[0, 0, 1, 1] // 4 - 1 = 3
[0, 0, 0, 0] // 4 & 3 = 0

class Solution:
    def hammingWeight(self, n: int) -> int:
        ans = 0
        while n:
            n &= n - 1
            ans += 1
        return ans

class Solution:
    def hammingWeight(self, n: int) -> int:
        ans = 0
        while n:
            n -= (n & -n)
            ans += 1
        return ans

public class Solution {
    // you need to treat n as an unsigned value
    public int hammingWeight(int n) {
        int ans = 0;
        while (n != 0) {
            n &= n - 1;
            ++ans;
        }
        return ans;
    }
}

public class Solution {
    // you need to treat n as an unsigned value
    public int hammingWeight(int n) {
        int ans = 0;
        while (n != 0) {
            n -= (n & -n);
            ++ans;
        }
        return ans;
    }
}

class Solution {
public:
    int hammingWeight(uint32_t n) {
        int ans = 0;
        while (n)
        {
            n &= n - 1;
            ++ans;
        }
        return ans;
    }
};

class Solution {
public:
    int hammingWeight(uint32_t n) {
        int ans = 0;
        while (n)
        {
            n -= (n & -n);
            ++ans;
        }
        return ans;
    }
};

func hammingWeight(num uint32) int {
	ans := 0
	for num != 0 {
		num &= num - 1
		ans++
	}
	return ans
}

func hammingWeight(num uint32) int {
	ans := 0
	for num != 0 {
		num -= (num & -num)
		ans++
	}
	return ans
}

/**
 * @param {number} n - a positive integer
 * @return {number}
 */
var hammingWeight = function (n) {
    let ans = 0;
    while (n) {
        n &= n - 1;
        ++ans;
    }
    return ans;
};

impl Solution {
    pub fn hammingWeight(n: u32) -> i32 {
        n.count_ones() as i32
    }
}

impl Solution {
    pub fn hammingWeight(mut n: u32) -> i32 {
        let mut res = 0;
        while n != 0 {
            res += n & 1;
            n >>= 1;
        }
        res as i32
    }
}

impl Solution {
    pub fn hammingWeight(mut n: u32) -> i32 {
        let mut res = 0;
        while n != 0 {
            n &= (n - 1);
            res += 1;
        }
        res
    }
}