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

 1 class Solution {
 2     /*
 3      * @param n: An integer
 4      * @return: True or false
 5      */
 6     public boolean checkPowerOf2(int n) {
 7         // write your code here
 8         boolean one = false;
 9         for (int i=0; i<31; i++) {
10             if ((n>>>i & 1) == 0) continue;
11             else if (!one) one = true;
12             else return false;
13         }
14         if (one) return true;
15         else return false;
16     }
17 };

Lintcode: O(1) Check Power of 2

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