Track Missing Package IDs from Out-of-Order Receipts

Question

The question asks the candidate to devise a solution for tracking missing package IDs from a series of out-of-order receipts.

Codemia · Accepted Answer

To address the problem of tracking missing package IDs from out-of-order receipts, we need to identify which package IDs are not present in the given list of receipts. The challenge lies in efficiently processing the receipts and determining the missing IDs, especially when they are provided in a non-sequential order.

1. **Input Representation**: We will represent the receipts as a list of integers, where each integer corresponds to a package ID. 
2. **Identify Range**: We need to determine the range of package IDs we are interested in, which can be inferred from the minimum and maximum IDs present in the receipts. 
3. **Tracking Missing IDs**: We will use a set to track the IDs present in the receipts and then compare this set against the expected range of IDs.

We can implement the solution as follows:

```python
def find_missing_package_ids(receipts):
    present_ids = set(receipts)
    min_id = min(present_ids)
    max_id = max(present_ids)
    missing_ids = []

for id in range(min_id, max_id + 1):
        if id not in present_ids:
            missing_ids.append(id)

return missing_ids
```
This function first creates a set of present package IDs, then iterates through the range from the minimum to maximum ID, checking which IDs are missing.

The time complexity of this solution is O(n) where n is the number of receipts, as we are iterating through the list to create the set and then through the range of IDs. The space complexity is also O(n) due to the storage of the set of present IDs.

Interviewers will look for clarity in the candidate's explanation of their approach, the efficiency of the algorithm, and how well they handle edge cases, such as when there are no receipts or when all IDs are present. They will also evaluate the candidate's coding style and ability to articulate their thought process.

Track Missing Package IDs from Out-of-Order Receipts

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