Binary Number with Alternating Bits

Given a positive integer, check whether it has alternating bits: namely, if two adjacent bits will always have different values. 

Input: 5
Output: True
Explanation:
The binary representation of 5 is: 101

Input: 11
Output: False
Explanation:
The binary representation of 11 is: 1011. 

bool hasAlternatingBits(int n) {
   
    if (n == 1 || n == 2) return true;
    int mask = n << 1;
    int flag = n ^ mask;
   
    flag = (n & 0x1)?(flag & (flag+1)):(flag & (flag+2));
   
    if (flag)
        return false;
    else
        return true;
}


or


bool hasAlternatingBits(int n) {
    int mask = n >> 1;
    int flag = n + mask;
   
    if (flag&(flag+1))
        return false;
    else
        return true;
}