Given a positive integer, check whether it has alternating bits: namely, if two adjacent bits will always have different values.
Example 1:
Input: 5
Output: True
Explanation:
The binary representation of 5 is: 101
Example 2:
Input: 7
Output: False
Explanation:
The binary representation of 7 is: 111.
Example 3:
Input: 11
Output: False
Explanation:
The binary representation of 11 is: 1011.
Example 4:
Input: 10
Output: True
Explanation:
The binary representation of 10 is: 1010.
解法1:
class Solution(object):
def hasAlternatingBits(self, n):
"""
:type n: int
:rtype: bool
"""
# check every bit is diff from last bit
last_bit = n & 1
n = n >> 1
while n:
bit = n & 1
if last_bit + bit != 1:
return False
last_bit = bit
n = n >> 1
return True
解法2: 移位再相加后,看是否为2的n次方
class Solution(object):
def hasAlternatingBits(self, n):
"""
:type n: int
:rtype: bool
"""
num = n + (n >> 1) + 1
return (num & (num-1)) == 0
解法3:直接使用bin函数
def hasAlternatingBits(self, n):
s = bin(n)
return '00' not in s and '11' not in s
标签:Alternating,693,return,Binary,Explanation,binary,Output,Input,bit From: https://blog.51cto.com/u_11908275/6381126