题目:
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:
根据丑陋数的定义,我们将给定数除以2、3、5,直到无法整除,也就是除以2、3、5的余数不再为0时停止。这时如果得到1,说明是所有因子都是2或3或5,如果不是1,则不是丑陋数。
程序:
class Solution {
public:
bool isUgly(int num) {
if(num<=0)
return 0;
int rem2 = num % 2;
int rem3 = num % 3;
int rem5 = num % 5;
while(rem2 == 0 || rem3 == 0 || rem5 == 0) {
if(rem2 == 0) {
num = num / 2;
} else if(rem3 == 0) {
num = num / 3;
} else {
num = num / 5;
}
rem2 = num % 2;
rem3 = num % 3;
rem5 = num % 5;
}
return num == 1;
}
};