add two-pointer-1 solutions

[nikhylw]

No description provided.

[super30admin]

Arrange Colors (sort_colors.py)

Strengths:

• Correctly implements the Dutch National Flag algorithm
• Clean, readable code with good variable naming
• Efficient inline swap using Python tuple unpacking
• Proper documentation of time and space complexity
• Achieves both one-pass and O(1) space requirements from the follow-up

Areas for minor improvement:

• Could add a docstring to the method explaining the algorithm
• The swap logic is correct, but the reference solution uses a helper method which could be useful for more complex swap logic (though not necessary here)

Overall, this is a solid implementation that matches the reference solution in both approach and quality.

VERDICT: PASS

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3 sum (three_sum.py)

The submitted solution addresses an entirely different problem. For the 3 Sum problem, you need to:

1. Work with an array input, not a binary tree
2. Find all unique triplets that sum to zero
3. Use an O(n²) approach (either sorting + two pointers, or hash set)
4. Handle duplicate triplets properly

Please review the problem statement again and implement a solution that processes the nums array to find all unique triplets summing to zero.

VERDICT: NEEDS_IMPROVEMENT

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Container With Most Water (container_with_water.py)

Strengths:

• Excellent implementation of the two-pointer technique
• Clear and readable code structure
• Correctly identified time and space complexity
• Efficient movement logic (always moving the pointer at the shorter line)

Areas for Improvement:

• Consider adding a brief docstring explaining the algorithm's logic for future reference
• Could add input validation for edge cases (though constraints handle this)

The solution demonstrates a solid understanding of the problem and an efficient algorithmic approach. Well done!

VERDICT: PASS