263. Ugly Number.md

263. Ugly Number

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leetcode Daily Challenge on November 18th, 2022.

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Difficulty : Easy

Related Topics : Math

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similar as leetcode Daily Challenge on July 4th, 2020. ---- 264. Ugly Number II

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

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Solution

• mine
  • Java
    • Runtime: 2 ms, faster than 34.40%, Memory Usage: 36.4 MB, less than 86.82% of Java online submissions

      // O(C)time   C is the count of factors
      // O(1)space
      public boolean isUgly(int num) {
          if(num <= 0){
              return false;
          }
          while(num % 2 == 0 || num % 3 == 0 || num % 5 == 0){
              if(num % 2 == 0){
                  num /= 2;
              }
              if(num % 3 == 0){
                  num /= 3;
              }
              if(num % 5 == 0){
                  num /= 5;
              }
          }
          return num == 1;
      }
      

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• the most votes

• Runtime: 2 ms, faster than 34.40%, Memory Usage: 38.3 MB, less than 12.27% of Java online submissions

  // O(C)time   C is the count of factors
  // O(1)space
  public boolean isUgly(int num) {
      for (int i=2; i<6 && num>0; i++)
          while (num % i == 0)
              num /= i;
      return num == 1;
  }
  

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