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.
这个题的主要思路就是将这个数中的关于2,3,5的素数因子除尽,才看看剩下的因子是不是等于1。如果等于1说明没有其他素数因子,则说明该数是ugly的。否则就不是
class Solution { public: bool isUgly(int num) { if (num == 0) return false; while (num % 2 == 0) num /= 2; while (num % 3 == 0) num /= 3; while (num % 5 == 0) num /= 5; return num == 1; } };