Day.11 Ugly Number(263)

问题描述
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1：只有对2的求模不为0 ，就不停的整除2.紧接着同样对3和5。最后判断num是否为1

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

思路2：同思路1，只是换种写法

var isUgly = function(num) {
    if(num === 0) {
        return false;
    }
    for (var p of [2, 3, 5])
    while (num && num % p === 0)
        num /= p;
    return num == 1;
};