Flatten a nested JSON object
Quick Overview
This question evaluates the ability to traverse and manipulate nested JSON-like structures, emphasizing concepts such as recursion or iterative traversal, array indexing, and path string construction; it tests data structures and serialization knowledge within the Coding & Algorithms domain and targets practical implementation skills for a software engineer role. It is commonly asked to assess how interviewees flatten hierarchical payloads for data processing or API normalization, reason about mixed object/array edge cases, and map hierarchical paths to primitive values.
Problem
You are given a JSON-like value representing an object that may contain:
- Objects / dictionaries (string keys)
- Arrays / lists
- Primitive values (string/number/boolean/null)
Return a flattened map from path to primitive value.
Path rules
-
Use
.to join object keys. -
Use
[i]for array indices. - The root has no leading separator.
Examples
Input
{
"a": 1,
"b": {"c": 2, "d": [3, 4]},
"e": [ {"f": 5}, 6 ]
}
Output
a -> 1
b.c -> 2
b.d[0] -> 3
b.d[1] -> 4
e[0].f -> 5
e[1] -> 6
Notes / constraints
-
Keys are strings and may contain any characters except
.and[](you may assume this to avoid escaping). -
The output can be returned as a dictionary/map of
string -> primitive. - Order does not matter.
Implement a function to perform this flattening.