题目描述
Write 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: 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.
解题思路1: 暴力求解
暴力求解, 将二进制数变成字符串, 遍历
示例代码1
def hammingWeight(n: int) -> int:
n = format(n, "032b")
count = 0
for c in n:
if c == "1":
count += 1
return count
解题思路2: 位运算
使用位运算, 每次拿到最后一位的1
示例代码2:
def hammingWeight(n: int) -> int:
count = 0
while n != 0:
n = n & (n - 1)
count += 1
return count
解题思路3: 内置函数
使用python的内置函数 count(), 直接一行代码搞定
示例代码3:
def hammingWeight(n: int) -> int:
return str(bin(n)).count("1")
