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Problems

Basics first, then the classics, then company-style assessments. Every problem has tests you run right here; multi-level ones unlock as you go. See the roadmap.

Advanced & competitive

Tree techniques

Binary lifting, LCA, Euler tours.

Binary lifting / LCA quiz
Euler tour of a tree quiz

Spot the pattern Quiz on all of it

8 problems

Advanced & competitive

Tree techniques Binary lifting, LCA, Euler tours.

Binary lifting / LCA

Basics: build the jump table basics py · c++ · java easy
Earliest ancestor born since a year py · c++ · java easy
K-th ancestor queries py · c++ · java medium
Lowest common boss py · c++ · java medium

Euler tour of a tree

Basics: entry and exit times (tin / tout) basics py · c++ · java easy
Upstream or downstream? py · c++ · java easy
Subtree sums with updates medium
Root-to-node path sums with updates medium