326. Power of three

Topic:

Given an integer, write a function to determine if it is a power of three.

Follow up:
Could do it without using any loop/recursion?

Answer:

Determines whether a number is a power of 3 and cannot be used in loops and recursion:

Since 3 is a prime number, so if one is a power of 3, then any of its approximations is also a power of 3.

So the idea is to find the largest 3 power of int, divided by the number we need to judge, and if the remainder is 0, the number is the power of 3.

Or a long long to find a power greater than the maximum value of int 3 is also possible.

1 classSolution {2  Public:3     BOOLIspowerofthree (intN) {4         intmax,m;5Max= (numeric_limits<int>:: Max) (); 6M=pow (3,((int) (log (max)/log (3))));7             return(n>0&& (m%n==0));8     }9};

Note: ^ is an XOR symbol in a bitwise operation, not a power-seeking symbol.

326. Power of three