An algorithm is a sequence of unambiguous steps to do a task. The challenges below require you to come up with algorithms to solve the problems.

Array
String
Dictionary
Dynamic Programming
Recursion
Tree

Binary Tree Preorder Traversal
Binary Tree Inorder Traversal
Binary Tree Postorder Traversal
Binary Tree Level Order Traversal
Same Tree
Univalued Binary Tree
Maximum Depth of Binary Tree
Path Sum
Sum of Left Leaves
Binary Tree Paths
Merge Two Binary Trees
Symmetric Tree