Given an integer, write a function to determine if it is a power of three.
Follow up:
Could you do it without using any loop / recursion?
Credits:
Special thanks to @dietpepsi for adding this problem and creating all test cases.
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c++ code:
class Solution {
public:
bool isPowerOfThree(int n) {
double t = log10((double)n) / log10(3.);
return (int)t == t;
}
};原文：http://blog.csdn.net/itismelzp/article/details/51378058