Create sum.py

[ViswaNikhitha]

Description

This pull request adds an efficient Python solution for the classic Two Sum problem.

The implementation uses a hash map (dictionary) to store previously seen values and their indices, allowing the solution to run in linear time.

Changes Made

• Implemented twoSum method inside a Solution class
• Used dictionary-based lookup to achieve O(n) time complexity
• Ensured compatibility with Python 2 and Python 3 (no type hints)

Approach

• Iterate through the array once
• For each element, compute the required complement (target - current value)
• Check if the complement exists in the dictionary
• Return indices once the pair is found

Time & Space Complexity

• Time Complexity: O(n)
• Space Complexity: O(n)

Testing

Test