Problem added

[megharaykar]

No description provided.

[super30admin]

Interview Problem : Two elements sum to target (Problem1.py)

Your submission shows good problem-solving skills by exploring multiple approaches. Here are some specific comments:

1. Brute-force solution: This is correct but inefficient. It's good to start with a straightforward solution, but for large inputs, it would be too slow.

2. Two-pass hashmap solution:

   • You create a hashmap that maps each value to its index. However, if there are duplicate values, the hashmap will store the last index for that value. This might cause issues if the duplicate is part of the solution (like in Example 3: [3,3] with target 6). But note: in your code, you delete entries after finding a pair, which is problematic.
   • You are adding both indices to res and then deleting the keys from the hashmap. This is unnecessary because the problem states there is exactly one solution. Also, if you delete the keys, you might miss valid pairs if the same number appears more than twice. For example, if the array is [2,2,2] and target is 4, your code might not work correctly.
   • Instead, you should simply return the indices as soon as you find a valid pair. Also, you should avoid using res as a list that you extend, because the problem guarantees exactly one solution, so you can return immediately.

3. One-pass hashmap solution: This is excellent! It is efficient (O(n) time) and handles duplicates correctly. You check for the complement before adding the current number to the hashmap, which avoids using the same element twice. This is the recommended optimal solution.

4. Code quality:

   • Your code is readable and well-structured. However, in the first two solutions, you have defined the same class Solution multiple times in the same file. This would cause a syntax error in Python. You should only define the class once. Typically, you would provide one solution per file, but for learning purposes, it's better to comment out previous solutions.
   • Also, in the one-pass solution, you have used type hints (nums: List[int]), which is good practice. However, you need to import List from typing for that to work. Your code doesn't show the import statement, so make sure to include it if you use type hints.

5. Efficiency: The one-pass hashmap solution is optimal. No further optimizations are needed.

Suggestions:

• For the two-pass solution, you can simplify it by not deleting entries and returning immediately when you find the complement (but note: you must ensure that the complement is not the same element). However, the one-pass solution is better.
• Always test your code with edge cases, such as duplicates and negative numbers.

VERDICT: PASS

---

Interview Problem: 0-1 Knapsack Problem

It appears there has been a misunderstanding. The problem you were asked to solve is the 0-1 Knapsack problem, but your solution is for the Two Sum problem. This suggests you may have confused the problem statements or worked on a different problem.

For the 0-1 Knapsack problem, you need to:

1. Understand the problem: Given weights and values of items, and a capacity, maximize the total value without exceeding the capacity, with the constraint that you can only take whole items (0-1 property).
2. Use dynamic programming: The standard solution involves creating a 2D DP table where dp[i][j] represents the maximum value achievable with the first i items and capacity j.
3. Implement the DP recurrence: For each item and each capacity, you decide whether to include the item (if it fits) or not, and take the maximum value option.

Your current solution for Two Sum is well-written and shows you understand different approaches (brute-force, hashmap) for that problem. However, it is not applicable here.

Please revisit the problem statement and implement the Knapsack solution using dynamic programming. You can refer to the reference solution provided for guidance on the structure and logic.

VERDICT: NEEDS_IMPROVEMENT