Implement Coin change And House Robber

[ayushcha2701]

No description provided.

[super30admin]

The Coin Change (CoinChange.java)

Strengths:

• Excellent use of dynamic programming, which is the optimal approach for this problem
• Clear comments explaining the DP transition logic
• Correct handling of edge cases (amount = 0 returns 0, impossible amounts return -1)
• Good time complexity analysis in comments
• Clean, readable code structure

Areas for Improvement:

• The outer loop for(int i = 1; i <= n; i++) could be simplified to an enhanced for-loop since the coin value isn't directly used as a loop counter
• Consider adding a check for amount == 0 at the beginning for early return (though the current solution handles it correctly)
• The variable name n for coins.length is slightly confusing since n typically represents the amount in coin change problems

Minor Note:
The reference solution uses recursion with exponential complexity, while your DP solution achieves polynomial time - this is a significant improvement and shows good understanding of algorithmic optimization.

VERDICT: PASS

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House Robber (HouseRobber.java)

Strengths:

• Good approach using space-optimized dynamic programming
• Clean variable naming and reasonable structure
• Attempted to handle edge cases (n == 1)

Areas for Improvement:

1. Fix the base case for n == 2: curr should be Math.max(prev, nums[1]), not Math.min
2. Fix the prev update inside the loop: change prev = curr; to prev = temp;
3. Consider adding comments to explain the DP logic for clarity
4. The initialization logic needs to handle all edge cases properly

The core DP recurrence is correct: dp[i] = max(dp[i-1], dp[i-2] + nums[i]), but the implementation has bugs in tracking the previous values.

VERDICT: NEEDS_IMPROVEMENT