LeetCode Js-263. Ugly Number

    AllenLi
    LeetCode Js-Number

    An ugly number is a positive integer whose prime factors are limited to 2, 3, and 5.
    Given an integer n, return true if n is an ugly number.

    一個不好看的數字是正整數，且質因數限制為 2、3、5。
給予一個整數 n，如果符合此條件則回傳正整數。

ex.尋找 2、3、5的共同公因數。

    Example 1:

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

    Example 2:

    Input: n = 1
Output: true
Explanation: 1 has no prime factors, therefore all of its prime factors are limited to 2, 3, and 5.

    Example 3:

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

    Solution:
    1. 運用 for of 來將陣列數值依序放入。
    2. 使用 while 來判斷，當 n 可以被整除，則將 n / p。
    當 n 沒法被整除，則 break。
    3. 回傳 n === 1 的結果。

    Code 1:

    var isUgly = function(n) {
    for (let element of [2, 3, 5]) {
        while (n && n % element === 0) {
            n /= element
        }
    }
    return n === 1;
};

    FlowChart:
    Example 1

    Input: n = 6
n = 6, element = 2, 3, 5
console.log(n, element, (n % element === 0))

step.1
6, 2, true
3, 2, false

step.2
3, 3, true
1, 3, false

step.3
1 5 false

return n === 1 //true

    Example 2

    Input: n = 1
n = 1, element = 2, 3, 5
console.log(n, element, (n % element === 0))

step.1
1 2 false

step.2
1 3 false

step.3
1 5 false

return  n === 1 //true

    Example 3

    Input: n = 14

step.1
14 2 true
7 2 false

step.2
7 3 false

step.3
7 5 false

return  n !== 1 //false

    Code 2:

    var isUgly = function (n) {
  if (n <= 0) return false;
  while (n % 2 === 0) n /= 2;
  while (n % 3 === 0) n /= 3;
  while (n % 5 === 0) n /= 5;
  return n === 1;
};

    Code 3:

    var isUgly = function (n) {
    if (n <= 0) return false;
    for (let element of [2, 3, 5]) {
        while (n % element === 0) {
            n /= element
        }
    }
    return n === 1;
};

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