Evaluate Ordered Access-Control Rules

Question

The question asks the candidate to evaluate a set of ordered access-control rules and determine whether to accept or block a given input based on these rules.

Codemia · Accepted Answer

To solve the problem, I will first outline the structure of the access-control rules and how they are evaluated. The rules will be processed in the order they are defined, and I will create a function that iterates through these rules to determine the final decision based on the input.

The algorithm will involve the following steps:
1. Parse the input rules to extract conditions and actions.
2. For each input, evaluate the rules in order until a decision is reached.
3. Implement boolean logic to handle complex conditions.

Here is a sample Python code implementation:
```python
def evaluate_access(rules, input_data):
    for rule in rules:
        condition, action = rule.split(' if ')
        if eval(condition.replace('amount', str(input_data['amount']))):
            return action.split()[0]  # 'ACCEPT' or 'BLOCK'
    return 'BLOCK'  # Default action
```
This function takes a list of rules and an input dictionary, evaluates each rule, and returns the appropriate action.

The time complexity of this algorithm is O(n), where n is the number of rules, since each rule is evaluated sequentially. The space complexity is O(1) as we are only storing the input data and the result.

I would validate the implementation with various test cases, such as:
1. Input: {'amount': 5000}, Rules: ['BLOCK if amount > 10000', 'ACCEPT if trusted_partner'] → Output: 'BLOCK'
2. Input: {'amount': 15000}, Rules: ['BLOCK if amount > 10000', 'ACCEPT if trusted_partner'] → Output: 'BLOCK'
3. Input: {'amount': 5000, 'trusted_partner': True}, Rules: ['BLOCK if amount > 10000', 'ACCEPT if trusted_partner'] → Output: 'ACCEPT'
This ensures the function behaves as expected under different scenarios.

I would also consider edge cases such as:
- No rules provided: should return 'BLOCK'.
- Invalid input data: should handle exceptions gracefully.
- Conflicting rules: should clarify how to prioritize them, potentially through a defined order.

Evaluate Ordered Access-Control Rules

Stripe

What the Interviewer Expects

Key Topics to Cover

How to Approach This

Possible Follow-up Questions

Sharpen Your Skills on Codemia

Sample Answer

Approach

Algorithm

Submit Your Answer

Stripe Software Engineer Interview Guide

Related Questions

Binary Search on graph

Count kth largest element in array

Find connected components in string

Merge Three Sorted strings

Binary Search on string