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  • LeetCode 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. 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.
    Credits:
    Special thanks to @jianchao.li.fighter for adding this problem and creating all test cases.

    这个在一些面试题目集里看到过,如何判断一个数是否是丑数的话还是容易的,之间用质因数分解的做法进行。

    class Solution {
    public:
        bool isUgly(int num) {
            if (num <= 0) {
                return false;
            }
            
            for (int f = 2; f <= 5; f++) {
                while (num % f == 0) {
                    num = num / f;
                }
            }
    
            return num == 1;
        }
    };
    

    直接一点可以这样:

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

    但是如果要输出一个区间内的丑数的话就不是那么简单了。

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  • 原文地址:https://www.cnblogs.com/lailailai/p/4769846.html
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