Flatten Nested Data | Dataford Interview Questions

LinkedIn frontend surfaces often receive deeply nested JSON-like data for profiles, jobs, and recommendations. Implement a function that flattens nested dictionaries and arrays into a single dictionary whose keys represent each value's path.

Formal Specification

Given data, a JSON-like dictionary or array, return a dictionary mapping dot-delimited path strings to scalar values. Dictionary keys become path components, and array positions become zero-based numeric components. A scalar is any value that is not a dictionary or array, including null and booleans. Empty dictionaries and arrays should be preserved as values at their paths. Input keys do not contain .. The root input is always a dictionary or array.

Use an iterative depth-first traversal so the function does not depend on Python's recursion limit.

Constraints

The input contains at most 10^5 total dictionaries, arrays, and scalar values.
Nesting depth can exceed 1,000.
Dictionary keys are strings and do not contain ..
Values are valid JSON-like values: dictionaries, arrays, strings, numbers, booleans, or null.
The root input is always a dictionary or array.

Function Signature

def flatten_nested(data):

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Problem