leetcode解题: Ugly Number (263)

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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.

解法1：暴力法

按照题意，ugly number一定是1，2，3，5几个数的乘积。那么用number不停的去整除2，3，5，如果发现不能整除，则不是ugly，如果能整除则继续直到为1或者出现不能整除的数为止。
C++

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class Solution {
public:
    bool isUgly(int num) {
        if (num <= 0) {
            return false;
        }
        while (num != 1) {
            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;
    }
};

Java

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