位1的个数(算法)

位1的个数(算法)

题目: 位1的个数
编写一个函数, 输入是一个无符号整数,
返回其二进制表达式中数字位为1的个数

3: 011 -> 2
5: 101 -> 2
8: 1000 -> 1

1.x % 2 ? 1 -> count++; x = x >> 1;
2.x = x & (x - 1)
11000 = 24
x = 11000
x - 1 = 10111

=> 10000

while x != 0:
	count++
	x = x & (x - 1)

python

def hamingWeight(self, n):
    rst = 0
    mask = 1
    for i in range(32):
        if n & mask:
            rst += 1
        mask = mask << 1
    return rst

java

int hammingWeight(uint32_t n) {
    int res = 0;
    for (; n; n &= n - 1)
        ++ res;
    return res;
}