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📦 Data Structures

Stacks, queues, hash maps and trees — implement and run them.

1
Lesson 1 — Stack
easy · 8 min
→2
Lesson 2 — Queue
easy · 8 min
→3
Lesson 3 — Hash map
medium · 9 min
→4
Lesson 4 — Sets
medium · 8 min
→5
Lesson 5 — Stacks
medium · 9 min
→6
Lesson 6 — Set operations
medium · 9 min
→7
Lesson 7 — Frequency map
medium · 9 min
→8
Lesson 8 — Graph as adjacency list
medium · 9 min
→9
Lesson 9 — Linked list
hard · 12 min
→10
Lesson 10 — Binary tree
hard · 12 min
→11
Lesson 11 — Queues
hard · 10 min
→12
Lesson 12 — Hash maps
hard · 11 min
→13
Lesson 13 — Linked list
hard · 12 min
→14
Lesson 14 — Binary tree
hard · 13 min
→15
Lesson 15 — Heap / priority
hard · 12 min
→16
Lesson 16 — Matrix traversal
hard · 11 min
→17
Lesson 17 — Mini project: unique words
hard · 12 min
→18
Lesson 18 — BFS traversal
hard · 11 min
→19
Lesson 19 — DFS traversal
hard · 11 min
→20
Lesson 20 — Union-Find
hard · 12 min
→21
Lesson 21 — Min-heap
hard · 11 min
→22
Lesson 22 — Trie (expert)
hard · 13 min
→23
Lesson 23 — Validate a BST
very hard · 15 min
→24
Lesson 24 — LRU cache
very hard · 15 min
→25
Lesson 25 — Ultimate: build a min-heap
★ ultimate · 20 min
→