[Leetcode] 693. Binary Number with Alternating Bits 解题报告

题目：

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：

练手题目。我们每次记录下n的最右边位上的值，然后再看其次右边位上的值，如果一样，就返回false；如果所有相邻位都不一样，就返回true。

代码：

class Solution {
public:
    bool hasAlternatingBits(int n) {
        int pre = n & 1;
        n = n >> 1;
        while (n > 0) {
            if ((n & 1) == pre) {
                return false;
            }
            pre = 1 - pre;
            n = n >> 1;
        }
        return true;
    }
};