Implement nested object path lookup
Company: Amazon
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: medium
Interview Round: Technical Screen
Implement a function `get(obj, path)` for a nested data structure composed only of maps and arrays.
Path rules:
- `.` accesses a map key
- `[i]` accesses an array index
- keys do not contain `.` or brackets
- example path syntax: `ab[1].c.d[2][13]`
Return the value at the given path. If any key is missing, an index is out of bounds, or the path does not match the actual type at some step, return `null`.
Examples:
- `get({"a": {"b": [10, 20]}}, "a.b[1]") -> 20`
- `get({"a": {"b": [10, 20]}}, "a.b[3]") -> null`
Write the function and analyze its time and space complexity.
Quick Answer: This question evaluates parsing and traversal of nested maps and arrays, robust error handling for missing keys and out-of-bounds indices, and reasoning about algorithmic time and space complexity.
Return the value at a dot/bracket path in nested dictionaries and arrays, or None if the path is invalid.
Constraints
- Map keys do not contain dots or brackets
Examples
Input: ({'a': {'b': [10, 20]}}, 'a.b[1]')
Expected Output: 20
Explanation: Prompt example.
Input: ({'a': {'b': [10, 20]}}, 'a.b[3]')
Expected Output: None
Explanation: Out-of-range index.
Input: ({'ab': [{'c': 5}]}, 'ab[0].c')
Expected Output: 5
Explanation: Object inside array.
Input: ({'a': 1}, 'a.b')
Expected Output: None
Explanation: Type mismatch.
Hints
- Tokenize the path, then walk the current object by token type.