CanSolak Personal Blog

Flattening Nested Dictionaries

Ever needed to write your own JSON or XML parser? Probably no. There are ready-to-use implementations in almost all programming languages. I also have not think about it till last week. Then, I am asked to implement a method to flatten nested dictionaries. This led me thoughts on possible issues while implementing such parser.

Last week, I am asked to implement a nested dictionary flattener method in an interview I had. Given a sample input-output dictionary pair, interviewer asked me to implement my solution in language of my choice. I usually implement solutions with C++11 in interviews. I immediately realized that I would need to deal with map<string,void*>. Then I changed the editor to Python and exploit the recurrence and built-in isinstance() method. The implementation above is made by me assuming it is not allowed to manipulate the input dictionary. Otherwise, I would follow a different strategy for this problem. I also added simple corner-case checks during interview to pass all test cases. The flattenDict() directory successfully returns the same result as below. In case you wonder why I immediately change to Python from C++11, the reason is the ease of using isinstance() method instead of dealing dynamic casting of void pointers in C++. There might be a compiler specific solution in C++ for this problem, I might write on it in the following posts.
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Istanbul, 2018