Lintcode: O(1) Check Power of 2

Using O(1) time to check whether an integer n is a power of 2.
Example
For n=4, return true

For n=5, return false

Challenge
O(1) time

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这道题考察bit manipulation. 1的个数只能有1个才是power of 2. 主要是要注意Integer.MIN_VALUE，这个只有一个1，但是是false

class Solution {
    /*
     * @param n: An integer
     * @return: True or false
     */
    public boolean checkPowerOf2(int n) {
        // write your code here
        boolean one = false;
        for (int i=0; i<31; i++) {
            if ((n>>>i & 1) == 0) continue;
            else if (!one) one = true;
            else return false;
        }
        if (one) return true;
        else return false;
    }
};