98 
Validate Binary Search Tree 
Medium 
Tree

Depthfirst Search

99 
Recover Binary Search Tree 
Hard 
Tree

Depthfirst Search

100 
Same Tree 
Easy 
Tree

Depthfirst Search

101 
Symmetric Tree 
Easy 
Tree

Depthfirst Search

Breadthfirst Search

104 
Maximum Depth of Binary Tree 
Easy 
Tree

Depthfirst Search

105 
Construct Binary Tree from Preorder and Inorder Traversal 
Medium 
Array

Tree

Depthfirst Search

106 
Construct Binary Tree from Inorder and Postorder Traversal 
Medium 
Array

Tree

Depthfirst Search

108 
Convert Sorted Array to Binary Search Tree 
Easy 
Tree

Depthfirst Search

110 
Balanced Binary Tree 
Easy 
Tree

Depthfirst Search

112 
Path Sum 
Easy 
Tree

Depthfirst Search

113 
Path Sum II 
Medium 
Tree

Depthfirst Search

114 
Flatten Binary Tree to Linked List 
Medium 
Tree

Depthfirst Search

116 
Populating Next Right Pointers in Each Node 
Medium 
Tree

Depthfirst Search

117 
Populating Next Right Pointers in Each Node II 
Medium 
Tree

Depthfirst Search

124 
Binary Tree Maximum Path Sum 
Hard 
Tree

Depthfirst Search

129 
Sum Root to Leaf Numbers 
Medium 
Tree

Depthfirst Search

130 
Surrounded Regions 
Medium 
Depthfirst Search

Breadthfirst Search

Union Find

199 
Binary Tree Right Side View 
Medium 
Tree

Depthfirst Search

Breadthfirst Search

257 
Binary Tree Paths 
Easy 
Tree

Depthfirst Search

337 
House Robber III 
Medium 
Tree

Depthfirst Search

366 
Find Leaves of Binary Tree 
Medium 
Tree

Depthfirst Search

513 
Find Bottom Left Tree Value 
Medium 
Tree

Depthfirst Search

Breadthfirst Search

515 
Find Largest Value in Each Tree Row 
Medium 
Tree

Depthfirst Search

Breadthfirst Search

559 
Maximum Depth of Nary Tree 
Easy 
Tree

Depthfirst Search

Breadthfirst Search

834 
Sum of Distances in Tree 
Hard 
Tree

Depthfirst Search

863 
All Nodes Distance K in Binary Tree 
Medium 
Tree

Depthfirst Search

Breadthfirst Search

872 
LeafSimilar Trees 
Easy 
Tree

Depthfirst Search

897 
Increasing Order Search Tree 
Easy 
Tree

Depthfirst Search

968 
Binary Tree Cameras 
Hard 
Dynamic Programming

Tree

Depthfirst Search

971 
Flip Binary Tree To Match Preorder Traversal 
Medium 
Tree

Depthfirst Search

979 
Distribute Coins in Binary Tree 
Medium 
Tree

Depthfirst Search

988 
Smallest String Starting From Leaf 
Medium 
Tree

Depthfirst Search

1026 
Maximum Difference Between Node and Ancestor 
Medium 
Tree

Depthfirst Search

1028 
Recover a Tree From Preorder Traversal 
Hard 
Tree

Depthfirst Search

1110 
Delete Nodes And Return Forest 
Medium 
Tree

Depthfirst Search

1123 
Lowest Common Ancestor of Deepest Leaves 
Medium 
Tree

Depthfirst Search

1145 
Binary Tree Coloring Game 
Medium 
Tree

Depthfirst Search

1192 
Critical Connections in a Network 
Hard 
Depthfirst Search

1203 
Sort Items by Groups Respecting Dependencies 
Hard 
Depthfirst Search

Graph

Topological Sort

1245 
Tree Diameter 
Medium 
Tree

Depthfirst Search

Breadthfirst Search

1302 
Deepest Leaves Sum 
Medium 
Tree

Depthfirst Search

1315 
Sum of Nodes with EvenValued Grandparent 
Medium 
Tree

Depthfirst Search

1319 
Number of Operations to Make Network Connected 
Medium 
Depthfirst Search

Breadthfirst Search

Union Find

1376 
Time Needed to Inform All Employees 
Medium 
Depthfirst Search

1377 
Frog Position After T Seconds 
Hard 
Depthfirst Search

1391 
Check if There is a Valid Path in a Grid 
Medium 
Depthfirst Search

Breadthfirst Search

1766 
Tree of Coprimes 
Hard 
Math

Tree

Depthfirst Search

Breadthfirst Search
