Trees Ladder

This ladder should make the rooted-tree viewpoint automatic, because many later techniques only become easy once parent, depth, and subtree meaning feel natural.

Who This Is For

Use this ladder if:

• tree problems still feel like generic graph problems
• rooting and subtree language still causes hesitation
• later topics like LCA and tree DP feel disconnected

Warm-Up

• rooting a tree
• subtree sizes
• tree diameter

Target skill:

• move cleanly between rooted and unrooted viewpoints

Core

• Euler tour intuition
• subtree aggregation
• tree DP basics

Target skill:

• recognize the repeated tree invariants that later algorithms reuse

Stretch

• VOSTRIP
• MTREECOL
• VMWTREE
• flatten subtree logic into range-like orderings

Target skill:

• prepare tree problems for LCA, tree DP, path queries, and range-based reductions
• recognize when a rooted tree is really a precedence structure for a greedy schedule

Exit Criteria

You are ready to move on when:

• you can compute parent, depth, and subtree size in one traversal
• you know when the unique-path property is the reason the solution works
• later tree topics feel like extensions rather than fresh starts

External Practice

• CSES Tree Algorithms
• USACO Guide
• OI Wiki - Tree DP

Tutorial Link

• Trees