263.Ugly Number
An ugly number is a positive integer whose prime factors are limited to 2, 3, and 5.
Given an integer n, return true if n is an ugly number.
Example 1:
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| Input: n = 6
Output: true
Explanation: 6 = 2 × 3
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Example 2:
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| Input: n = 1
Output: true
Explanation: 1 has no prime factors, therefore all of its prime factors are limited to 2, 3, and 5.
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Example 3:
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| Input: n = 14
Output: false
Explanation: 14 is not ugly since it includes the prime factor 7.
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个人解答：
时间复杂度：O(logn)
空间复杂度：O(1)
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| class Solution {
public:
bool isUgly(int n) {
if(n <= 0)return false;
while(n != 1) {
if(n%2 == 0)n /= 2;
else if(n%3 == 0)n /= 3;
else if(n%5 == 0)n /= 5;
else return false;
}
return true;
}
};
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优化：
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| class Solution {
public:
bool isUgly(int n) {
if (n <= 0) {
return false;
}
vector<int> factors = {2, 3, 5};
for (int factor : factors) {
while (n % factor == 0) {
n /= factor;
}
}
return n == 1;
}
};
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