LN : leetcode 263 Ugly Number

lc 263 Ugly Number

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lc 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.

analysation##

Use recursion, then the problem will be much easier.

solution

bool isUgly(int num) {
  if (num <= 0)
  return 0;
  if (num == 1)
  return 1;
  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 0;
}