Trees
Problems on trees, including traversals, depths and subtree sizes, diameters and centres, lowest common ancestors, binary trees, minimum spanning trees, centroid decomposition, and dynamic programming on subtrees.
The Graphs section of the library covers depth-first search, breadth-first search, Kruskal's and Prim's algorithms. Related problem sets are under Graphs, Depth-first search and Disjoint set union.
Problems
Colored Wizards#188
Very easy
Evolution#223
Very easy
Regions#293
Hard
Tree#468
Very easy
Tree Games#659
Very easy
Is it a Tree?#977
Very easy
Get a tree#978
Very easy
Handbags#1164
Medium
Cartesian tree#1314
Medium
Pre, in and post#1513
Medium
Constructing BST#1516
Very easy
Hide That Number#1626
Very easy
Locks and keys#1827
Very hard
Ancestor#1941
Easy
Tree#2021
Very easy
Girls' Celebration#2053
Very hard
Happy Painting!#2054
Very hard
Rujia Liu loves Wario Land!#2058
Very hard