Problem 5

Config Merge with Deletions

MEDIUMBUILD

Hash Map+2

Implement merge_configs(base, override) that deep-merges two Python dicts and returns a new dict. Keys present in only one dict are kept as-is. If both values are dicts, merge recursively. Otherwise the override value wins, except if the override value is None, the key is removed from the result. Lists are never merged; the override list replaces the base list. Do not mutate base or override.

Examples

Example 1

Input

base = {"a": 1, "b": {"x": 1, "y": 2}}
override = {"b": {"y": 99, "z": 3}}

Output

{"a": 1, "b": {"x": 1, "y": 99, "z": 3}}

Example 2

Input

base = {"a": 1, "b": {"x": 1}, "c": 3}
override = {"b": None, "c": {"k": 1}}

Output

{"a": 1, "c": {"k": 1}}

Note

None deletes the key; a non-dict override replaces the base dict.

Constraints

Values may be dicts, lists, strings, numbers, booleans, or None
Nesting depth is at most 20

Follow-up

How would you detect and reject cyclic references in input objects?

Hints

Console output will appear here...