263. 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.

Example 1:

Input: 6
Output: true
Explanation: 6 = 2 × 3

Example 2:

Input: 8
Output: true
Explanation: 8 = 2 × 2 × 2

Example 3:

Input: 14
Output: false 
Explanation: 14 is not ugly since it includes another prime factor 7.

Note:

1. 1 is typically treated as an ugly number.
2. Input is within the 32-bit signed integer range: \([−2^{31}, 2^{31} − 1]\).

思路：

Solution (C++):

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

性能：

Runtime: 0 ms  Memory Usage: 5.9 MB

思路：

Solution (C++):

性能：

Runtime: ms  Memory Usage: MB