Daily coding problems solutions using C++

Implement a PrefixMapSum class with the following methods:

insert(key: str, value: int): Set a given key's value in the map. If the key already exists, overwrite the value. sum(prefix: str): Return the sum of all values of keys that begin with a given prefix.

For example, you should be able to run the following code:

mapsum.insert("columnar", 3)
assert mapsum.sum("col") == 3

mapsum.insert("column", 2)
assert mapsum.sum("col") == 5