Adding DP-1 (coin-change)

[nikhylw]

No description provided.

[super30admin]

The Coin Change (W2_6_322_coin_change_tabulation.py)

Your solution is on the right track and correctly implements the tabulation method for the coin change problem. Here are some suggestions for improvement:

• Instead of using 999999 as a placeholder for infinity, consider using float('inf') or amount + 1 (since the maximum number of coins cannot exceed amount). This makes the code more robust and easier to understand.
• Improve variable names: Use n for the number of coins and m for the amount to align with common conventions. Also, dp table dimensions are (n+1) x (m+1), so you can name rows = len(coins) and cols = amount.
• You can optimize the space complexity by using a 1D DP array. Since each row only depends on the previous row and the current row, you can use a single array of size amount+1 and update it iteratively. This reduces space from O(n * amount) to O(amount).
• Add a check for the base case when amount is 0 at the beginning to return 0 immediately, though your current solution handles it correctly.
• Consider adding comments to explain the DP transitions for better readability.

Here is an example of how you can write the optimized version with 1D DP:

def coinChange(self, coins: List[int], amount: int) -> int:
    dp = [float('inf')] * (amount + 1)
    dp[0] = 0
    for coin in coins:
        for j in range(coin, amount + 1):
            dp[j] = min(dp[j], dp[j - coin] + 1)
    return dp[amount] if dp[amount] != float('inf') else -1

Overall, your solution is correct and efficient, but with the above improvements, it can be more robust and efficient in terms of space.

VERDICT: PASS

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House Robber

It appears you may have submitted code for a different problem. Please review the problem statement for "House Robber" and implement a solution specific to that problem. For House Robber, you can use a dynamic programming approach where dp[i] represents the maximum amount robbed up to house i, with choices to include or exclude the current house.

For example, the recurrence is: dp[i] = max(dp[i-1], nums[i] + dp[i-2])

Start by understanding the problem correctly and ensure your code matches the problem requirements. If you were working on Coin Change previously, make sure to switch contexts appropriately.

VERDICT: NEEDS_IMPROVEMENT