Core
Graphs & Trees
Traversal is the core skill: once you can BFS and DFS a grid, tree, or graph fluently, most graph problems reduce to a known template plus a twist.
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Upgrade- Invert Binary TreeEasy
- Maximum Depth of Binary TreeEasy
- Binary Tree Level Order TraversalMedium
- Number of IslandsMedium
- Clone GraphMedium
- Course ScheduleMedium