In Python you can save a substantial amount of memory when creating a large number of objects by defining __slots__.

In the Python code: https://www.hackerrank.com/challenges/contacts/submissions/code/28219710 changing the Node class from:

class Node:
    def __init__(self):
        self.ch={}
        self.count=0

To:

class Node(dict):
    __slots__ = ['count']
    def __init__(self):
        self.count=0

Where Node is subclassed from dict and __slots__ is set manually to have a counter, saves enough memory to allow the code to run without a segmentation fault.