Think in patterns.
Solve like it’s the interview.

hand-picked DSA problems in C#, Java, Python, C++ and JavaScript. Run your code, climb the leaderboard and keep your streak alive.

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37problems
12core patterns
5languages
2 Lakh+learners trained

Bubble sort

ArraysO(n²)Running

Compare neighbours, swap when out of order.

Inorder traversal

TreesDFSO(n)

Visit order:

Breadth-first search

GraphsQueueO(V+E)

Level order:

Longest common subsequence

Dynamic ProgrammingO(mn)

dp[i][j] = best length for the first i and j characters.

Browse by pattern

Master the idea once, solve the whole family.

Arrays Strings Linked List Trees Graphs DP Recursion Sorting Searching Hashing Stack Queue

All Easy Medium Hard

#	Title	Acceptance	Difficulty
1	Compare Leaf Traversal Tree · Traversal · Binary Tree	77.95%	Medium
2	Inorder Successor in BST Tree · Traversal · Binary Tree	60.12%	Medium
3	Kth Largest Element in BST Tree · Traversal · Binary Tree	70.53%	Medium
4	Construct Tree from Inorder + Postorder Tree · Traversal · Binary Tree	65.12%	Medium
5	Top View of Binary Tree Tree · Traversal · Binary Tree	60.21%	Medium
6	Convert Sorted Array to BST Tree · Traversal · Binary Tree	74.56%	Medium
7	Find Distance Between Two Nodes Tree · Traversal · Binary Tree	62.45%	Medium
8	All Paths With Given Sum Tree · Traversal · Binary Tree	74.23%	Medium
9	Maximum Root to Leaf Path Sum Tree · Traversal · Binary Tree	72.15%	Medium
10	Minimum Depth of Binary Tree Tree · Traversal · Binary Tree	60.25%	Medium
11	Construct Tree from Inorder + Preorder Tree · Traversal · Binary Tree	70.00%	Medium
12	Right View of Binary Tree Tree · Traversal · Binary Tree	74.36%	Medium
13	Lowest Common Ancestor in BST Tree · Traversal · Binary Tree	70.50%	Medium
14	Kth Smallest Element in BST Tree · Traversal · Binary Tree	76.77%	Medium
15	Delete Node In BST Tree · Traversal · Binary Tree	65.20%	Medium
16	Validate BST Tree · Traversal · Binary Tree	45.23%	Medium
17	Lowest Common Ancestor of Binary Tree Tree · Traversal · Binary Tree	78.59%	Medium
18	Root To Leaf Path Sum Tree · Traversal · Binary Tree	78.56%	Medium
19	Diameter of Binary Tree Tree · Traversal · Binary Tree	73.45%	Medium
20	Check Binary Tree Is Balanced Tree · Traversal · Binary Tree	78.95%	Medium
21	Check if Tree is Symmetric Tree · Traversal · Binary Tree	74.98%	Medium
22	Check if Two Trees are Identical Tree · Traversal · Binary Tree	76.59%	Medium
23	Count Leaf Nodes In Binary Tree Tree · Traversal · Binary Tree	74.59%	Medium
24	Count Total Nodes in Binary Tree Tree · Traversal · Binary Tree	75.68%	Medium
25	Height / Max Depth of Binary Tree Tree · Traversal · Binary Tree	75.36%	Medium
26	Binary Tree Zigzag Level Order Traversal Tree · Recursion · Traversal	71.48%	Medium
27	Permutation of A String String · Recursion	66.00%	Medium
28	Longest Palindromic Substring String	34.80%	Medium
29	Form Anagram Groups String · Hashing	69.80%	Medium
30	Length of the longest substring String	50.00%	Medium
31	First Occurrence In A String String	50.08%	Medium
32	Longest Common Subsequence Array · String · Dynamic Programming	50.00%	Medium
33	K-Pangrams String · Hashing	20.91%	Medium
34	Stepping Numbers BFS · DFS	48.44%	Medium
35	Course Schedule Graph · BFS · DFS	51.77%	Medium
36	Strings Rotations String	43.83%	Medium
37	Unique Permutations String	46.50%	Medium

Practice that builds the habit

Three steps, repeated every day.

1
Pick a pattern
Start from an idea such as two pointers or BFS, then move through easy, medium and hard.
2
Code and run
Write in your language, run on sample cases and submit against every hidden test.
3
Climb the board
Every solve earns points. Keep a daily streak and see where you stand this month.