Create pointer2.java

[Praniksha123]

No description provided.

[super30admin]

Merge Sorted Array (pointer2.java)

Your solution for the Merge Sorted Array problem is excellent! You correctly implemented the three-pointer technique from the end, which is the optimal approach. Key strengths include:

1. Correct Algorithm: The merge logic properly handles both arrays being exhausted at different times
2. Efficient: No extra space used, O(m+n) time complexity achieved
3. Clean Code: Well-structured with clear variable naming and proper indentation
4. Good Comments: The approach explanation is clear and helpful

Note: Your submission file also includes solutions for two other problems (removeDuplicates and searchMatrix). If these were intended for different problems, that's fine, but make sure to submit only the relevant solution for each problem.

VERDICT: PASS

---

Search a 2D Matrix II

EVALUATION

Correctness

The student's solution for Problem 3 (Search a 2D Matrix II) is correct. It implements the optimal approach of starting from the top-right corner and eliminating either a row or column at each step. This works because:

• If current element > target, all elements to the left are also smaller (move left)
• If current element < target, all elements below are also larger (move down)

This correctly handles all cases and will find the target if it exists.

Time Complexity

• Reference Solution: O(m log n) - performs binary search on each row
• Student Solution: O(m + n) - worst case traverses one full row and one full column

The student's solution is more efficient in time complexity. The reference solution has O(m log n) which could be worse than O(m + n) when m and n are both large.

Space Complexity

Both solutions use O(1) extra space, which is optimal.

Code Quality

The student's code is:

• Clean and well-structured
• Uses meaningful variable names (r, c for row/column)
• Has clear comments explaining the approach
• Follows good Java conventions

Efficiency

The student's approach is actually more optimal than the reference solution for this specific problem. The top-right corner approach is the canonical optimal solution for this matrix property.

---

FEEDBACK

Strengths:

1. ✅ Correctly implements the optimal O(m + n) algorithm for this problem
2. ✅ Clean, readable code with good variable naming
3. ✅ Well-documented with comments explaining the logic
4. ✅ Efficient use of space (O(1))

Areas for Improvement:

1. The student submitted solutions for 3 different problems, but only Problem 3 is relevant to the "Search a 2D Matrix II" task. Future submissions should focus on the specific problem assigned.
2. The reference solution uses binary search per row (O(m log n)), but the student's approach (O(m + n)) is actually superior for this problem due to the matrix's sorted properties. This shows good algorithmic thinking!

Note: The first two problems (removeDuplicates and merge) are not related to the Search a 2D Matrix problem. Please ensure you submit solutions only for the assigned problem.

---

The student's solution for Problem 3 (Search a 2D Matrix II) is correct, efficient, and well-implemented. It uses an optimal O(m + n) algorithm that is actually better than the reference O(m log n) solution. The code is clean and well-documented.

VERDICT: PASS

---

Remove Duplicates from Sorted Array II

Strengths:

• Clear documentation and comments explaining each approach
• Good variable naming conventions
• Problems 2 and 3 are solved optimally with correct approaches

Areas for Improvement:

1. Problem 1 (Critical): The HashMap approach violates the O(1) space constraint. The problem explicitly requires modifying the input array in-place with only O(1) extra memory. The reference two-pointer solution is the intended approach.
2. Problem 1: While the solution produces correct output for this specific problem, using a HashMap for an in-place array problem is generally not the right pattern to follow.
3. Consider learning the two-pointer technique for sorted array problems - it's more space-efficient and commonly used in these scenarios.

---

VERDICT: NEEDS_IMPROVEMENT