LeetCode 2520. Count the Digits That Divide a Number

Given an integer num, return the number of digits in num that divide num.

An integer val divides nums if nums % val == 0.

Example 1:

Input: num = 7 
Output: 1 
Explanation: 7 divides itself, hence the answer is 1.

Example 2:

Input: num = 121 
Output: 2 
Explanation: 121 is divisible by 1, but not 2. Since 1 occurs twice as a digit, we return 2.

Example 3:

Input: num = 1248 
Output: 4 
Explanation: 1248 is divisible by all of its digits, hence the answer is 4.

Constraints:

1. 1 <= num <= 10^9
2. num does not contain 0 as one of its digits.

效能

• Time complexity: O(n)
• Space complexity: O(n)
• Runtime: 17 ms
• Memory: 26.6 MB

題解

Weekly Contest 326，Easy。

給一組數字，分解成一個一個數字，找出可以整除原本數字的數量。

var num = 12345; 
// 數字：      [1, 2, 3, 4, 5] 
// 可以被整除： [O, X, O, X, O] => return 3

最佳解

把原本的 int 變成可以跑 for 或 foreach 的物件，一個一個比對就行。

var count = 0; 
var nums = num.ToString(); 
 
foreach (var n in nums) 
{ 
    var current = Convert.ToInt32(n.ToString()); 
     
    if (current == 0) 
    { 
        // 除數不能是 0 
        continue; 
    } 
 
    if (num % current == 0) 
    { 
        count++; 
    } 
} 
 
return count;

參考資料

• 2520. Count the Digits That Divide a Number