Description
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.
Solution
Bit manipulation
class Solution {
public boolean hasAlternatingBits(int n) {
// If n has alternating bits, then (n>>1) + n must be like 111...11.
long add = (long) n + (n >> 1) + 1;
return (add & (add - 1)) == 0;
}
}
