adding bfs-1 solutions

[nikhylw]

Solution 1 - W5_1_level_order_traversal.py
Solution 2 - W5_3_course_schedule.py

[super30admin]

Level Order Traversal in Binary tree (W5_1_level_order_traversal.py)

Strengths:

• Excellent optimization by using deque with popleft() instead of list.pop(0) - demonstrates awareness of Python performance characteristics
• Well-commented code with clear self-notes
• Clean, readable implementation that matches the reference solution's logic
• Proper handling of edge cases (empty tree)

Areas for Improvement:

• The space complexity comment "O(n/4)" is mathematically incorrect - the maximum queue size in a complete binary tree is approximately n/2, not n/4. For a balanced tree, the maximum width is typically around n/2.
• Could add type hints for better code documentation (e.g., List[List[int]] return type is already present but could be more complete)
• The solution is functionally equivalent to the reference and doesn't need significant changes

VERDICT: PASS

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Scheduling Courses (W5_3_course_schedule.py)

Strengths:

• Clean implementation of topological sort using BFS approach
• Good variable naming (indegrees, outdegree_graph, etc.)
• Proper handling of edge cases
• Early return optimization when all courses have indegree 0
• Correct use of deque for efficient queue operations

Areas for Improvement:

• The early return if count == numCourses: return True inside the while loop is redundant since the final return statement handles this case
• Could simplify count = count + 1 to count += 1
• The comment # self-note: Do not use outdegree_graph.get[curr] is unnecessary for production code
• Could add type hints for better code documentation
• The final return False is unreachable in some cases due to the early return inside the loop, but it's good defensive programming

Minor Optimizations:

• The if dependencies: check is good but could be combined with the for loop using for dep in dependencies or []:
• Consider using collections.defaultdict(list) to simplify the hashmap initialization

Overall, this is a solid solution that correctly implements the topological sort algorithm with good readability.

VERDICT: PASS