Backtracking-1 Assignment completed

[Hriday-A]

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[super30admin]

Combination Sum (combination_sum.java)

Strengths:

• Excellent use of backtracking with in-place modification, which is more memory-efficient than creating deep copies
• Clear code structure with well-labeled sections (base, logic, action, recurse, backtrack)
• Good understanding of the problem, evident from having explored two different approaches
• Proper handling of all base cases
• Correctly identifies that the same index is used when an element is chosen (allowing reuse)

Areas for Improvement:

• The time complexity analysis could be more precise. The actual complexity is O(C * n) where C is the number of valid combinations (at most 150 per constraints), and n is the average length of combinations. The current O(2^(m+n)) is a loose upper bound.
• Consider adding early pruning optimization: if candidates are sorted, you can stop exploring when target becomes negative early in the recursion.

VERDICT: NEEDS_IMPROVEMENT

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Operations and expressions (expression_and_operator.java)

Strengths:

• Correct implementation of the backtracking algorithm
• Properly handles the multiplication operator precedence using the tail/calc technique
• Good use of StringBuilder with setLength for efficient backtracking
• Correctly prevents leading zeros in multi-digit numbers
• Clean and concise implementation

Areas for Improvement:

• Variable naming could be more descriptive (e.g., savedLength instead of le)
• Adding comments explaining the multiplication logic would improve readability
• The comment // why - sign ?? suggests confusion about why tail is negated for subtraction - this should be understood: when we track tail as negative for subtraction, it allows the multiplication formula to work correctly (calc - tail + tail * curr)

Minor suggestions:

• Consider adding a comment explaining the calc - tail + tail * curr formula for multiplication
• The code could benefit from more descriptive variable names for maintainability

VERDICT: PASS