Count Failing, Passing and Distinction Scores from Percentage Thresholds

You are given an array of integers `scores`, where the index is a student ID and the value is that student's exam score as a percentage. Each student is graded as follows: - below 50: **failed**, - from 50 to 80 inclusive: **passed**, - above 80: **passed with distinction**. Return an array of three integers: the number of students who failed, the number who passed, and the number who passed with distinction, in that order. ### Function Signature ```python def grade_counts(scores: list[int]) -> list[int]: ``` ### Rules - A score of exactly 50 or exactly 80 counts as passed; a score of exactly 81 counts as passed with distinction. - Every student falls into exactly one of the three groups, so the three counts sum to `len(scores)`. - An empty array returns `[0, 0, 0]`. ### Constraints - `0 <= len(scores) <= 100000` - `0 <= scores[i] <= 100` ### Examples **Example 1** - Input: `scores = [30, 50, 65, 80, 81, 95, 49]` - Output: `[2, 3, 2]` - Explanation: 30 and 49 fail; 50, 65 and 80 pass; 81 and 95 pass with distinction. **Example 2** - Input: `scores = [100, 100]` - Output: `[0, 0, 2]` - Explanation: Both students scored above 80. **Example 3** - Input: `scores = []` - Output: `[0, 0, 0]` - Explanation: With no students, every count is zero.