DP-1 problem solution

[Simranb10]

DP-1 problem solution

[super30admin]

The Coin Change (CoinChange.java)

Strengths:

• Correctly implements bottom-up dynamic programming
• Good use of sentinel value (amount + 1) for initialization
• Clean and readable code structure
• Significantly better time complexity than the reference recursive solution
• Proper handling of edge cases

Areas for Improvement:

• The outer loop iterates for(int i = 1; i <= coins.length; i++) but doesn't use i directly in the loop body - it could be simplified or the iteration variable could be used more meaningfully
• Consider adding a check for amount == 0 at the start for early return (though the current code handles it correctly since dp[0] = 0)
• The comment about time complexity could be clearer with better variable naming

VERDICT: PASS

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House Robber (HouseRobber.java)

Strengths:

1. Excellent use of dynamic programming, transforming an exponential problem into a linear one
2. Clean, readable code with meaningful variable names
3. Proper handling of edge cases (single house scenario)
4. Correct recurrence relation implementation

Areas for Improvement:

1. Space optimization: Since dp[i] only depends on dp[i-1] and dp[i-2], you can reduce space from O(n) to O(1) by using just two variables
2. Consider adding a brief comment explaining the recurrence relation for future maintainability
3. The class could benefit from a main method or test cases to demonstrate usage

Suggested Optimization:

// O(1) space version
int prev2 = nums[0];
int prev1 = Math.max(nums[0], nums[1]);
for(int i = 2; i < n; i++) {
    int current = Math.max(prev1, prev2 + nums[i]);
    prev2 = prev1;
    prev1 = current;
}
return prev1;

VERDICT: PASS