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`.

Example 1:

``````Input: 6
Output: true
Explanation: 6 = 2 × 3
``````

Example 2:

``````Input: 8
Output: true
Explanation: 8 = 2 × 2 × 2
``````

Example 3:

``````Input: 14
Output: false
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: [−231,  231 − 1].

``````class Solution {
public:
bool isUgly(int num) {
while (num >= 2) {
if (num % 2 == 0) num /= 2;
else if (num % 3 == 0) num /= 3;
else if (num % 5 == 0) num /= 5;
else return false;
}
return num == 1;
}
};
``````

``````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;
}
};
``````

Github 同步地址：

https://github.com/grandyang/leetcode/issues/263

Super Ugly Number

Ugly Number II

Happy Number

Count Primes

https://leetcode.com/problems/ugly-number/

https://leetcode.com/problems/ugly-number/discuss/69225/My-2ms-java-solution

https://leetcode.com/problems/ugly-number/discuss/69214/2-4-lines-every-language

https://leetcode.com/problems/ugly-number/discuss/69332/Simple-java-solution-with-explanation

https://leetcode.com/problems/ugly-number/discuss/69308/Java-solution-greatest-divide-by-2-3-5

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