Question
Given a range [m, n]
where 0 <= m <= n <= 2147483647
, return the bitwise AND of all numbers in this range, inclusive.
Example 1:
Input: [5,7]
Output: 4
Example 2:
Input: [0,1]
Output: 0
Solution
One bit can be set if and only if both m and n have this bit set, and the range is not larger than the number of this bit.
class Solution(object):
def rangeBitwiseAnd(self, m, n):
"""
:type m: int
:type n: int
:rtype: int
"""
res = 0
bit = 1
diff = n - m + 1
while m >= bit:
if m & bit != 0 and n & bit != 0 and diff <= bit:
res += bit
bit *= 2
return res