adding interview-2 solutions

[nikhylw]

solution 1 (Two sum) - W2_two_sum.py
solution 2 (0/1 knapsack) - W2_01knapsack.py

[super30admin]

Interview Problem : Two elements sum to target (W2_two_sum.py)

Strengths:

• Excellent use of hashmap to achieve O(N) time complexity, surpassing the O(N²) reference solution
• Correct algorithm logic that properly handles the complement lookup
• Good variable naming and readable code structure
• Well-commented time/space complexity analysis

Areas for Improvement:

1. Add from typing import List at the top of the file to properly import the type hint
2. Consider returning directly when found: return [i, hashmap[complement]] instead of appending to a result list - this is slightly more efficient and cleaner
3. The current implementation always iterates through the entire array even after finding the answer (though it returns immediately). This is a minor point.

Overall, this is a solid implementation that demonstrates good understanding of the hashmap technique for this classic problem.

VERDICT: NEEDS_IMPROVEMENT

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Interview Problem: 0-1 Knapsack Problem (W2_01knapsack.py)

Strengths:

• Correct implementation of the 0-1 Knapsack DP approach
• Clean, readable code with descriptive variable names
• Good use of comments explaining the logic
• Accurate complexity analysis included as comments
• Proper handling of base cases (i==0 or j==0)
• Clear separation of "choose" and "don't choose" logic

Areas for Improvement:

• The variable choose is initialized to 0, which works but could be slightly misleading. Consider initializing it conditionally or using a more explicit approach.
• The solution could benefit from a test case demonstration in the main block (like the reference solution has) to show the algorithm in action.
• While the 2D DP approach is correct, the student could explore space optimization (1D DP) as an advanced topic to reduce space complexity from O(n*W) to O(W).

Overall, this is a solid implementation that demonstrates good understanding of dynamic programming concepts.

VERDICT: PASS