693. Binary Number with Alternating Bits

Posted 2021-02-28 dysjtu1995

Problem:

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.

思路：

Solution (C++):

bool hasAlternatingBits(int n) {
    long long m = n >> 1;
    return ((m+n) & (m+n+1)) == 0;
}

性能：

Runtime: 0 ms??Memory Usage: 5.8 MB

思路：

Solution (C++):

bool hasAlternatingBits(int n) {
    n ^= n >> 2;
    return (n & (n-1)) == 0;
}

性能：

Runtime: 0 ms??Memory Usage: 5.9 MB