693. 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.

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.

含义：让我们判断一个二进制数的1和0是否是交替出现的

 

    public boolean hasAlternatingBits(int n) {
//        char[] chs = Integer.toBinaryString(n).toCharArray();
//        if (chs.length<2) return true;
//        char evenChar = chs[0];
//        char oddChar = chs[1];
//        for(int i=2;i<chs.length;i++)
//        {
//            if (i%2 ==0)
//            {
//                if (evenChar != chs[i]) return false;
//            }else
//                if (oddChar != chs[i]) return false;
//        }
//        return true;
        int a=n<<1;
        int b= n^a;
        char[] chs = Integer.toBinaryString(b).toCharArray();
        for (int i=0;i<chs.length-1;i++) if (chs[i] != '1') return false;
        boolean result = n==(n&b);
        return result;
    }