Ugly Number

Problem:

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.

Solution:

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

Another Approach:

int maxDivide(int a, int b)

{

  while (a%b == 0)

   a = a/b;

  return a;

}  

 

/* Function to check if a number is ugly or not */

int isUgly(int no)

{

  no = maxDivide(no, 2);

  no = maxDivide(no, 3);

  no = maxDivide(no, 5);

   

  return (no == 1)? 1 : 0;

}