Find the Largest Rating Threshold Supported by K Instances
Company: Amazon
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: hard
Interview Round: Online Assessment
Given an array of integer instance ratings, return the largest integer `k` such that at least `k` instances have ratings greater than or equal to `k`.
### Input and Output
- Input: an array of integer ratings, one value per instance.
- Output: one integer, the maximum qualifying `k`. Return `0` when no positive `k` qualifies.
- `k` cannot exceed the number of instances. A rating equal to `k` meets the threshold.
- For this practice version, an empty array has answer `0`.
### Example 1
```text
ratings = [3, 0, 6, 1, 5]
answer = 3
```
Three ratings are at least `3`: `3`, `6`, and `5`.
### Example 2
```text
ratings = [0, 0]
answer = 0
```
Overview: Find the largest k for which at least k instance ratings are at least k, handling threshold equality and the zero-answer case.
Given an array of integer instance ratings, return the largest integer `k` such that at least `k` instances have ratings greater than or equal to `k`.
### Input and Output
- Input: an array of integer ratings, one value per instance.
- Output: one integer, the maximum qualifying `k`. Return `0` when no positive `k` qualifies.
- `k` cannot exceed the number of instances. A rating equal to `k` meets the threshold.
- For this practice version, an empty array has answer `0`.
### Example 1
```text
ratings = [3, 0, 6, 1, 5]
answer = 3
```
Three ratings are at least `3`: `3`, `6`, and `5`.
### Example 2
```text
ratings = [0, 0]
answer = 0
```
Constraints
- ratings is a finite array of integers and may be empty.
- No rating-magnitude or array-size bound is supplied.
- Return the largest k between 0 and the number of instances with at least k ratings greater than or equal to k.
Examples
Input: ([3, 0, 6, 1, 5],)
Expected Output: 3
Explanation: Three ratings reach at least three, but fewer than four reach four.
Input: ([0, 0],)
Expected Output: 0
Explanation: No positive threshold has enough qualifying instances.
Hints
- A threshold cannot exceed the number of instances.
- A rating equal to the threshold counts toward it.