LeetCode 263.Ugly Number

Write a program to check whether a given number is an ugly number.

Ugly numbers are positive numbers whose prime factors only include 2, 3, 5. For example, 6, 8 are ugly while 14 is not ugly since it includes another prime factor 7.

Note that 1 is typically treated as an ugly number.

思路：判断一个数是否为“ugly number”，只须要判断该数可否有限次的被2，3，5整除，且1也为“ugly number”，即最后只要最后的结果为1即为“ugly number”。

language-javascript

/**
 * @param {number} num
 * @return {boolean}
 */
var isUgly = function(num) {
    if(num <= 0){
        return false
    }
    if(num == 1){
        return true;
    }
    while(num % 2 === 0){
        num/=2;
    }
    while(num % 3 === 0){
        num/=3;
    }
    while(num % 5 === 0){
        num/=5;
    }
    return (num == 1)? true : false;
};