Problem

Given a positive integer n (1 <= n <= 10^18). Check whether a number has exactly three distinct factors, return true if it has exactly three distinct factors, otherwise false.

Example

Given n = 9, return true

Given n = 10, return false

Solution

public class Solution {    /**     * @param n: the given number     * @return:  return true if it has exactly three distinct factors, otherwise false     */    public boolean isThreeDisctFactors(long n) {        // write your code here        long fac = (long) Math.sqrt(n);        if (fac * fac != n) return false;        for (long i = 2; i < fac; i++) {            if (n % i == 0) return false;        }        return true;    }}