Choosing a multiple of n (with.Java)

This is an article about the problem of “Selecting a multiple of n.”

As I solve coding test problems, I look back on the problems I solved and look into different solution methods to learn more.

Let’s look at the problem first.

problem

When the integer n and the integer array numlist are given as parameters, complete the solution function to return an array with numbers that are not multiples of n removed from numlist.

Restrictions

• 1 ≤ n ≤ 10,000
• 1 ≤ size of numlist ≤ 100
• 1 ≤ elements of numlist ≤ 100,000

Input/Output Example

My solution to the problem

class Solution {
     public int[] solution(int n, int[] numlist) {
         int cnt = 0;
         for(int x : numlist){
             if(x % n == 0){
                 cnt++;
             }
         }
         int[] answer = new int[cnt];
         int idx = 0;
         for(int i = 0; i < numlist.length; i++){
             if(numlist[i] % n == 0){
                 answer[idx++] = numlist[i];
             }
         }
         return answer;
     }
}

Solution explanation

• cnt: A variable for counting the number of numbers divisible by n. The initial value is set to 0.
• for-each loop: Remove x from the numlist array one by one and repeat.
• If the remainder when x is divided by n is 0, that is, if x is divisible by n, cnt is increased.
• Result array (answer) initialization: Use cnt to specify the size of the result array answer.
• Initialization of index variable (idx): Initialize the index variable idx to 0 to store the value in the result array answer.
• for loop: Repeats the numlist array using index i.
• If the remainder is 0 when numlist[i] is divided by n, that is, if numlist[i] is divisible by n, numlist[i] is stored in answer[idx] and idx is increased by 1.