Variables, operators, input, conditionals, loops, lists, and functions — 8 exercises plus a bonus battle.
Summation, reverse an array, remove duplicates, and find the minimum — algorithm review.
TreeNode class, recursive DFS, traversals, and path problems — with an interactive BST visualizer.
Heap data structure, priority queues, and practical exercises using Python's heapq module.
Frequency counting, Top-K Frequent Elements, and CCC Bronze Count problem.
Master backtracking — subsets, combination sum, and permutations.
2D arrays, four-directions pattern, DFS flood fill and region counting, BFS shortest path.
Build adjacency lists, detect cycles with DFS, and find valid course orderings.
Halve the search space at every step — classic search, first occurrence, insert position, and range queries.
Search, insert, validate, and find the kth smallest — using the left < root < right property.
Shortest paths on weighted graphs using a min-heap priority queue — with an interactive step-by-step visualizer.