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 × 3Example 2:
Input: 8 Output: true Explanation: 8 = 2 × 2 × 2Example 3:
Input: 14 Output: false Explanation:14is not ugly since it includes another prime factor7.
Note:
1is typically treated as an ugly number.- Input is within the 32-bit signed integer range: [−231, 231 − 1].
丑数I。题意是判断一个正整数是否为ugly number。ugly number的定义是这个数字只能被2,3,5三者的乘积所得到。
就按照思路做即可，判断能否被2,3,5整除即可。代码如下
时间O(n)
空间O(1)
JavaScript实现
1 /** 2 * @param {number} num 3 * @return {boolean} 4 */ 5 var isUgly = function(num) { 6 if (num === 1) return true; 7 if (num === 0) return false; 8 while (num % 2 === 0) num = Math.floor(num / 2); 9 while (num % 3 === 0) num = Math.floor(num / 3); 10 while (num % 5 === 0) num = Math.floor(num / 5); 11 return num === 1; 12 };
Java实现
1 class Solution { 2 public boolean isUgly(int num) { 3 if (num == 1) return true; 4 if (num == 0) return false; 5 while (num % 2 == 0) num /= 2; 6 while (num % 3 == 0) num /= 3; 7 while (num % 5 == 0) num /= 5; 8 return num == 1; 9 } 10 }