Find Missing Observations — LeetCode 2028 Python Solution

The problem

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.

Example

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.

Python solution

class Solution:
    def missingRolls(self, rolls: List[int], mean: int, n: int) -> List[int]:
        m = len(rolls)
        s = (n + m) * mean - sum(rolls)
        if s > n * 6 or s < n:
            return []
        ans = [s // n] * n
        for i in range(s % n):
            ans[i] += 1
        return ans

Complexity

Pattern: Math and Number Theory

Find the closed form, the invariant, or the modular identity — and skip the loop entirely. LeetCode 2028. Find Missing Observations is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Math.

The math and number theory guide has the Python template for the pattern and the 485 LeetCode problems that use it.

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