Excuse me, that’s MY SPOT!

Every Jack has his Jill.
Every man can expect to have his partner.

Recently, I did some interesting array-related interview questions. The problem description starts like this or similar: Given an array nums containing n numbers in the range [0, n] … and asks you to find duplicate/missing numbers.

Here is one of the problem description

Given an array of integers where 1 ≤ a[i] ≤ n (n = size of array), some elements appear twice and others appear once.
Find all the elements of [1, n] inclusive that do not appear in this array.
For example,
Input:
[4,3,2,7,8,2,3,1]
Output:
[5,6]

The SO-EASY Solution

One can quickly come up with a solution which uses an additional array to store each of the element at its correct spot.

class Solution {
    public List<Integer> findDisappearedNumbers(int[] nums) {
        int n = nums.length;
        int[] temp = new int[n];
        for (var num : nums) {
            temp[num - 1] = num;
        }
        List<Integer> res = new ArrayList<>();
        for (int i = 0; i < n; ++i) {
            if (temp[i] == 0) {
                res.add(i + 1);
            }
        }
        return res;
    }
}

That’s it! Thanks for reading ;) I’m kidding. This might be the appetizer or warm-up for the interview and your interviewer…