Completed Binary Search 1

[Sanket-S-Kale]

No description provided.

[super30admin]

Search inside a Rotated Sorted Array (Problem1.py)

Looking at this evaluation, I need to assess the student's solution against the given problem about searching in a rotated sorted array.

Critical Issue

The student solved the wrong problem.

The problem title and description clearly state this is about searching in a Rotated Sorted Array (LeetCode #33), but the student's code solves the Search a 2D Matrix problem (LeetCode #74).

The reference solution uses a modified binary search that handles the rotated array by determining which half is sorted at each step.

The student's solution treats a 2D matrix as a 1D array and searches for a target value, which is completely different from the rotated array problem.

Evaluation

1. Correctness: ❌ The solution does not solve the given problem at all. It solves a different problem entirely.

2. Time Complexity: N/A for this problem since it's solving a different problem. For the problem it solves (2D matrix search), O(log(m*n)) is optimal.

3. Space Complexity: O(1) - good for the problem it solves.

4. Code Quality: The code is well-structured and readable for the problem it addresses.

5. Efficiency: Appropriate for its intended problem.

Feedback

Strengths:

• The code is clean, well-documented, and follows good practices
• Uses proper binary search with low + (high - low) // 2 to avoid overflow
• Good variable naming and clear logic flow
• Correctly handles the 2D matrix search problem

Areas for Improvement:

• Major: You solved the wrong problem. Always read the problem statement carefully and ensure your solution matches the exact requirements.
• The solution needs to implement the rotated sorted array search algorithm, which involves determining which half of the array is sorted at each step and adjusting the search space accordingly.

What you should do:
Implement the rotated sorted array search using a modified binary search that:

1. Finds which portion of the array (left or right of mid) is sorted
2. Determines if the target lies within the sorted portion
3. Adjusts the search boundaries accordingly

The code quality is good, but the solution does not address the given problem. You need to implement the correct algorithm for searching in a rotated sorted array.

VERDICT: NEEDS_IMPROVEMENT

---

Search Inside a Sorted Array whose Length is unknown (Problem2.py)

• Strengths: The code is clean, well-commented, and correctly implements binary search for rotated arrays. Variable naming is clear, and the logic for determining which half is sorted is properly implemented.
• Weaknesses: The solution addresses the wrong problem entirely. The original problem requires:
  1. Using an ArrayReader interface instead of direct array access
  2. Exponential search to find bounds for an unknown-length array
  3. Standard binary search on the found range
• Recommendation: To improve, the student should carefully read problem descriptions and ensure the solution matches the exact requirements. The core binary search logic is correct and can be adapted for the actual problem by incorporating the ArrayReader interface and exponential search phase.

VERDICT: NEEDS_IMPROVEMENT

---

Search a 2D Matrix (Problem3.py)

Strengths:

• The code is clean, well-structured, and well-commented
• Binary search implementation within the found range is correct
• Good variable naming and clear phase separation

Weaknesses:

• Major Issue: The solution solves a completely different problem than what was asked
• The student implemented "Search in Infinite Sorted Array" instead of "Search a 2D Matrix"
• The solution uses an ArrayReader API that doesn't exist in the actual problem
• No attempt to treat the 2D matrix as a flattened sorted array
• The exponential search phase is unnecessary for a fixed-size matrix

What was needed:
The correct approach for "Search a 2D Matrix" is to:

1. Treat the m×n matrix as a single sorted array of length m*n
2. Map index i to matrix[i/n][i%n]
3. Perform standard binary search on indices [0, m*n-1]

Recommendation:
The student needs to re-read the problem statement carefully and implement the correct algorithm for the 2D matrix search problem. The solution should directly perform binary search on the matrix without the exponential search phase.

VERDICT: NEEDS_IMPROVEMENT