Medium
🔀 Sorting
Bubble Sort
The classic teaching tool. You'll never ship this slow O(n²) sort to production, but watching adjacent elements swap teaches invaluable loop boundary mechanics.
Time: O(n²)
Space: O(1)
15 min
Start Advanced
AI WisdomAll tracks
Track
Advanced
Engineers refining problem solving
Start thinking algorithmically. Watch how recursion builds up call stacks, see sorting in real-time, and finally actually understand why Big O notation matters in prod.
Sorting algorithms
Recursion & trees
Time complexity
10 algorithms in this track
Hard
🔀 Sorting
Merge Sort
Divide, branch, and conquer. Watch the recursion split arrays down to single elements, then seamlessly stitch them back into sorted perfection. A fast, stable O(n log n) engine.
Time: O(n log n)
Space: O(n)
18 min
Start Hard
🔀 Sorting
Quick Sort
The workhorse sort. Pick a pivot, partition around it, and recurse. It's fast, boasts legendary cache locality, but see why bad pivots cause worst-case nightmares.
Time: O(n log n) avg, O(n²) worst
Space: O(log n)
18 min
Start Hard
🔀 Sorting
Heap Sort
Visualize the max-heap. Pull the highest priority element out and re-balance. It guarantees O(n log n) even in worst-cases, heavily utilized in priority-queue systems.
Time: O(n log n)
Space: O(1)
20 min
Start Hard
🕸 Graph
Breadth-First Search
Explore outward like a ripple. See Breadth-First Search utilize a queue to guarantee the shortest path in unweighted networks—essential for pathfinding.
Time: O(V + E)
Space: O(V)
18 min
Start Hard
🕸 Graph
Depth-First Search
Plunge deep before backtracking. Depth-First Search stacks recursive calls, perfect for exhausting possibilities in maze solving or topological sorting.
Time: O(V + E)
Space: O(V)
18 min
Start Hard
🌳 Trees
Binary Tree Traversal
Navigating the node network. See the dramatic differences when you process roots before, between, or after children (pre/in/post-order).
Time: O(n)
Space: O(h)
15 min
Start Medium
Hash Maps
Two Sum
The most famous leetcode question. See how building an on-the-fly hash map trades a tiny bit of RAM to nosedive the time complexity down to O(n).
Time: O(n)
Space: O(n)
12 min
Start Medium
Stacks
Valid Parentheses
The ultimate stack test. Watch pushing openers and popping them when a closer arrives—this is literally how your code compiler checks syntax.
Time: O(n)
Space: O(n)
12 min
Start Medium
🔁 Recursion
Fibonacci (Recursive)
Exponential explosion. Watch the call tree branch out horrifyingly out of control. An excellent warning on why raw recursion desperately needs memoization.
Time: O(2ⁿ) naive, O(n) memoized
Space: O(n)
15 min
Start