題目鏈接
tag:
- Easy辆亏；
question：
??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 is typically treated as an ugly number.
- Input is within the 32-bit signed integer range: [?231, 231 ? 1].
思路：
??本題讓我們檢測(cè)一個(gè)數(shù)是否為丑陋數(shù)饮戳，所謂丑陋數(shù)就是其質(zhì)數(shù)因子只能是2,3,5吮廉。那么最直接的辦法就是不停的除以這些質(zhì)數(shù)，如果剩余的數(shù)字是1的話就是丑陋數(shù)了毅臊，有兩種寫法矾端，如下所示：
C++ 解法一：
class Solution {
public:
bool isUgly(int num) {
if (num < 1) return false;
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 true;
}
};
C++ 解法二：
class Solution {
public:
bool isUgly(int num) {
if (num < 1) return false;
while (num % 2 == 0) num /= 2;
while (num % 3 == 0) num /= 3;
while (num % 5 == 0) num /= 5;
return num == 1;
}
};
