Lettcode_263_Ugly Number

Lettcode_263_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.

思路：

（1）該題題意為給定一個數，判斷該數是否為“丑數”。

（2）這道題很基礎。丑數是因子只含有2、3、5的數。所以只需對這三個數循環取余判斷即可。這裡不再累贅。

（3）詳情見下方代碼。希望本文對你有所幫助。

public class Ugly_Number {

	public static void main(String[] args) {
		for (int i = 0; i < 100; i++) {
			System.err.println(i + == + isUgly(i));
		}
	}

	// 2 3 5
	public static boolean isUgly(int num) {

		if (num == 1)
			return true;

		while (num >= 2 && num % 2 == 0) {
			num = num / 2;
		}

		while (num >= 3 && num % 3 == 0) {
			num = num / 3;
		}

		while (num >= 5 && num % 5 == 0) {
			num = num / 5;
		}

		return num == 1 ? true : false;
	}

}