2028. Find Missing Observations

this problem is how to find the edge case

[3,5,3]
5
3

[6,3,4,3,5,3]
1
6

T: O(m+n)

S: O(n)

class Solution {
    public int[] missingRolls(int[] rolls, int mean, int n) {
        int m = rolls.length;
        int total = 0;
        for (int roll : rolls) {
            total += roll;
        }
        int leftSum = mean*(m+n) - total;
        int leftMean = leftSum/n;
        if (leftMean <= 0 || leftMean > 6) {
            return new int[]{};
        }
        int remainder = leftSum%n;
        if (leftMean == 6 && remainder != 0) {
            return new int[]{};
        }
        int[] res = new int[n];
        Arrays.fill(res, leftMean);
        for (int i = 0; i < remainder; i++) {
            res[i]++;
        }
        return res;
    }
}