Question
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.
Difficulty:Medium
Category:Bit-Manipulation
Analyze
这个对于中间分割数据, 相同的两位不一样的情况下, 数据 n
和 n >> 1
求异或
的话, 就可以得到全为 11111111
的数据, 我们只要判断得到的数所有位都是1就可以了.
Solution
class Solution {
public:
bool hasAlternatingBits(int n) {
int a = (n ^ (n >> 1));
if (a == INT_MAX) return true;
return (a & long(a + 1)) == 0;
}
};