Backtracking-1 Solution

[indrasena483]

No description provided.

[super30admin]

Combination Sum (Problem1.java)

Strengths:

• Excellent implementation of the backtracking pattern with proper backtracking (path.remove)
• More memory-efficient than the reference solution by avoiding unnecessary ArrayList copies
• Clean code structure with clear comments explaining each step
• Correct base case handling and recursion termination

Areas for Improvement:

• The time complexity analysis could be more precise. The actual complexity is closer to O(n * 2^n) where n is the number of candidates, as each candidate can be chosen or not chosen at each step
• Consider adding early termination optimization: if candidates are sorted, you could prune branches where remaining candidates are too large to contribute to the remaining target

Minor Note:

• The comment "Time Complexity : O(2^(m+n))" is slightly imprecise. A more accurate representation would be O(n * 2^n) or O(2^n) where n is the number of candidates, as the target value primarily affects the depth of recursion rather than the branching factor

VERDICT: PASS

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Operations and expressions (Problem2.java)

Strengths:

• Clean backtracking implementation with proper action/recurse/backtrack pattern
• Correct handling of multiplication precedence using the tail variable
• Proper early termination for invalid numbers with leading zeros
• Good use of StringBuilder for efficient string manipulation
• Clear separation of base case and recursive logic

Areas for Improvement:

• The comment "top level" is slightly misleading; it would be clearer to say "first number (no operator)" or "starting number"
• Consider adding a brief comment explaining why we track the "tail" value (for handling multiplication precedence)
• The solution could benefit from early pruning: if calc exceeds target significantly during addition/subtraction, we could potentially prune branches (though this requires careful handling due to multiplication)

VERDICT: PASS