Add: Stack with Min Implementation in Python

[saishmungase]

Description

This PR adds an implementation of a LIFO Stack that supports an additional get_min() operation in O(1) time complexity, as requested in the data_structures README (Medium Priority).

• File Added: Python/data_structures/stack/stack_with_min.py
• Functionality: Implements standard stack operations (push, pop, top, is_empty, size) plus get_min() using an auxiliary stack to track minimums.
• Follows LIFO principle.

Algorithm Description (Included in code comments)

Uses a main stack for elements and an auxiliary stack (_min_stack). When pushing, if the new item is <= the top of _min_stack, it's pushed onto _min_stack. When popping, if the popped item matches the top of _min_stack, it's popped from _min_stack too. get_min() simply returns the top of _min_stack.

Complexity Analysis (Included in code comments)

• Time Complexity:
  • Push: O(1)
  • Pop: O(1)
  • Top: O(1)
  • GetMin: O(1)
• Space Complexity: O(n)

Checklist

• Code follows the project's contributing guidelines (folder structure, naming).
• Code includes data structure description comment.
• Code includes time and space complexity analysis.
• Code is tested (includes doctests).
• Commit message follows the specified format.
• This PR adds one specific data structure implementation.

[github-actions]

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[github-actions]

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✅ Passed - File naming and structure look good!

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[saishmungase]

Hey @Pradeepsingh61 , @Karanjot786 Can You Please check this PR ?