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l263 ugly number

admin 11月 13, 2020 0

题目描述

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.

解题思路

判断n是否能被2，3，5整除，如果不可以直接返回false
如果可以将n替换为n/[2,3,5]后，再进行判断

Go实现1

func (num int) bool {
    if num<=0{
        return false
    }
    if num == 1 {
        return true
    }

    for num >1 {
        flag:= false
        for _,x := range []int{2,3,5}{
            if num%x==0 {
                num = num/x
                flag=true
            }
        }
        if !flag {
            return false
        }
    }

    return true

}

Go实现2

func (num int) bool {
    if num<=0{
        return false
    }
    if num == 1 {
        return true
    }

    for _,x := range []int{2,3,5}{
        for num%x==0 {
            num = num/x
        }
    }

    return num == 1
}