循环

class Solution {
public:
    bool isPowerOfTwo(int n) {
        for(int i = 0; i <= 31; i++){
            if(pow(2,i) == n){
                return true;
            }
        }
        return false;

    }
};

class Solution {
public:
    bool isPowerOfTwo(int n) {
        return n > 0 && (n & (n-1)) == 0;
    }
};

class Solution {
public:
    bool isPowerOfTwo(int n) {
        return n > 0 && (n & (-n)) == n;
    }
};