LeetCode in Kotlin

2028. Find Missing Observations

Medium

You have observations of n + m 6-sided dice rolls with each face numbered from 1 to 6. n of the observations went missing, and you only have the observations of m rolls. Fortunately, you have also calculated the average value of the n + m rolls.

You are given an integer array rolls of length m where rolls[i] is the value of the ith observation. You are also given the two integers mean and n.

Return an array of length n containing the missing observations such that the average value of the n + m rolls is exactly mean. If there are multiple valid answers, return any of them. If no such array exists, return an empty array.

The average value of a set of k numbers is the sum of the numbers divided by k.

Note that mean is an integer, so the sum of the n + m rolls should be divisible by n + m.

Example 1:

Input: rolls = [3,2,4,3], mean = 4, n = 2

Output: [6,6]

Explanation: The mean of all n + m rolls is (3 + 2 + 4 + 3 + 6 + 6) / 6 = 4.

Example 2:

Input: rolls = [1,5,6], mean = 3, n = 4

Output: [2,3,2,2]

Explanation: The mean of all n + m rolls is (1 + 5 + 6 + 2 + 3 + 2 + 2) / 7 = 3.

Example 3:

Input: rolls = [1,2,3,4], mean = 6, n = 4

Output: []

Explanation: It is impossible for the mean to be 6 no matter what the 4 missing rolls are.

Constraints:

• m == rolls.length
• 1 <= n, m <= 105
• 1 <= rolls[i], mean <= 6

Solution

@Suppress("NAME_SHADOWING")
class Solution {
    fun missingRolls(rolls: IntArray, mean: Int, n: Int): IntArray {
        var n = n
        val m = rolls.size
        var msum = 0
        val res = IntArray(n)
        for (roll in rolls) {
            msum += roll
        }
        var totalmn = mean * (m + n) - msum
        if (totalmn < n || totalmn > n * 6) {
            return IntArray(0)
        }
        var j = 0
        while (totalmn > 0) {
            val dice = Math.min(6, totalmn - n + 1)
            res[j] = dice
            totalmn = totalmn - dice
            n--
            j++
        }
        return res
    }
}

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