Pattern: BFS (Trees + Graphs)

[sudosf]

Objective

Master breadth-first search on trees and graphs from the RisingBrain DSA sheet.

References

• Course section (BFS Trees): https://www.youtube.com/watch?v=Z_c4byLrNBU&t=2908s (0:48:28)
• Course section (BFS Graphs): https://www.youtube.com/watch?v=Z_c4byLrNBU&t=3036s (0:50:36)
• Sheet (Tree): https://www.risingbrain.org/sheet#tree
• Sheet (Graph): https://www.risingbrain.org/sheet#graph
• Parent course ticket: DSA Patterns course - AlgoMonster / freeCodeCamp #2

Pattern Description

Use a queue (ArrayDeque in Java). Process nodes level by level. Mark visited before enqueuing (graphs).

Sub-issues

#	Problem	Difficulty
1	Binary Tree Level Order Traversal	Medium
2	Binary Tree Right Side View	Medium
3	Binary Tree Zigzag Level Order Traversal	Medium
4	Number of Islands	Medium
5	Word Ladder	Hard

Notes

Language: Java
Use ArrayDeque, not LinkedList, as the queue.