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.

    Example 1:

    1. Input: 6
    2. Output: true
    3. Explanation: 6 = 2 × 3

    Example 2:

    1. Input: 8
    2. Output: true
    3. Explanation: 8 = 2 × 2 × 2

    Example 3:

    1. Input: 14
    2. Output: false 
    3. Explanation: 14 is not ugly since it includes another prime factor 7.

    Note:

    1. 1 is typically treated as an ugly number.
    2. Input is within the 32-bit signed integer range:263. Ugly Number (E) - 图1.

    题意

    判断一个数的因数是否只有2，3，5。

    思路

    除以所有的2，3，5，判断最后留下的数是不是1。

    代码实现

    1. class Solution {
    2.     public boolean isUgly(int num) {
    3.         // 特殊情况排除
    4.         if (num == 0) {
    5.             return false;
    6.         }
    8.         while (num % 2 == 0) {
    9.             num /= 2;
    10.         }
    11.         while (num % 3 == 0) {
    12.             num /= 3;
    13.         }
    14.         while (num % 5 == 0) {
    15.             num /= 5;
    16.         }
    17.         return num == 1;
    18.     }
    19. }