Implement Array-1: Self Product,and Diagonal and Spiral Matrix

[ashutosh-das-id]

No description provided.

[super30admin]

Product of Array Except Self (Product.java)

Evaluation

Correctness

The student's solution correctly solves the problem. It uses the standard two-pass approach:

1. First pass (left to right): Calculates the product of all elements to the left of each index
2. Second pass (right to left): Multiplies each element by the product of all elements to its right

This correctly produces the product of all elements except self at each position. The solution handles edge cases properly and produces the correct output for both example cases.

Time Complexity

O(n) - The solution uses two linear passes through the array, which is optimal for this problem. This is a significant improvement over the reference solution's O(n²) approach.

Space Complexity

O(1) extra space (excluding output array) - The solution uses only a few integer variables (rightProduct) and reuses the result array for both passes. This meets the follow-up requirement of O(1) extra space complexity. The reference solution claims O(1) but actually uses O(n) for the unused leftProduct array.

Code Quality

The code is well-structured and readable:

• Clear variable naming
• Logical flow with two distinct passes
• Comments explaining the approach
• Efficient use of the result array as both left product accumulator and final output

Minor issue: The leftProduct array is declared but never used, which is wasteful and potentially confusing.

Efficiency

The solution is highly efficient:

• Two linear passes instead of nested loops
• No division operation (as required)
• Minimal extra memory usage
• Early termination not needed as both passes must traverse the entire array

Feedback

Strengths:

1. Excellent time complexity (O(n)) - much better than the reference solution
2. Correctly achieves O(1) extra space complexity
3. Clean, readable code with good variable naming
4. Proper use of comments explaining the approach
5. Correctly handles the problem constraints

Areas for Improvement:

1. Remove the unused leftProduct array declaration - it serves no purpose and adds confusion
2. Consider adding a brief comment explaining why result[0] is initialized to 1
3. The initial comment block mentions O(1) space but the declared leftProduct array contradicts this - keep comments consistent with actual implementation

Overall Assessment:
This is a solid, efficient solution that meets all problem requirements and exceeds the reference solution in both time and space complexity. The only improvement needed is removing the unused array declaration.

VERDICT: PASS

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Diagonal Traverse (DiagonalMatrix.java)

Strengths:

1. Excellent input validation - handles null matrix and empty matrix cases gracefully
2. Clear and descriptive variable naming (rows, cols, up for direction)
3. Well-structured code with consistent formatting
4. Good comments explaining the boundary logic at each condition
5. Correct ordering of boundary checks (corner cases prioritized)
6. Follows standard coding conventions with proper braces style

Areas for minor improvement:

1. The comment header mentions "Three line explanation" but doesn't actually include it - could add a brief explanation
2. Could consider adding a brief comment about the diagonal order pattern for future maintainability

The solution is functionally equivalent to the reference solution and demonstrates solid understanding of the algorithm. The implementation is clean, readable, and efficient.

VERDICT: PASS

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Spiral Matrix (SpiralMatrix.java)

Strengths:

• The solution correctly implements the four-pointer boundary approach
• Clean and readable code structure
• Good use of descriptive variable names
• Proper handling of edge cases (when top > bottom or left > right)
• Well-documented with time/space complexity comments

Areas for Improvement:

• The solution is functionally equivalent to the reference solution and doesn't require significant changes
• Could add a brief comment explaining why the conditional checks (if (top <= bottom) and if (left <= right)) are necessary to prevent invalid traversals

VERDICT: PASS