u/FormalEmployee8680

You don't need to solve 1,000 LeetCode questions. You need to master these 25 DSA patterns.

Here is a full cheat sheet built from problems that kept repeating across 200+ MAANG+ interview experiences.

[1] Sliding window

LC: 3, 76, 209, 424, 567, 904

→ Use when the problem asks for a longest, shortest, or valid contiguous range.

[2] Two pointers

LC: 11, 15, 16, 18, 42, 167

→ Look for sorted arrays, pair conditions, or movement from both ends.

[3] Fast and slow pointers

LC: 19, 141, 142, 160, 234, 876

→ Best for linked-list cycles, middle nodes, and pointer gaps.

[4] Binary search

LC: 33, 34, 35, 153, 162, 704

→ Use when the search space is sorted or partially ordered.

[5] Binary search on answer

LC: 410, 774, 875, 1011, 1283, 1482

→ Guess an answer, test feasibility, then shrink the range.

[6] Hashing

LC: 1, 49, 128, 217, 242, 347

→ Use for quick lookup, frequency counting, grouping, and duplicate checks.

[7] Prefix sum

LC: 303, 523, 560, 724, 930, 974

→ Convert repeated range-sum work into constant-time lookups.

[8] Difference array

LC: 370, 1094, 1109, 1893, 1943, 2381

→ Use when many updates affect entire ranges.

[9] Monotonic stack

LC: 84, 85, 496, 503, 739, 907

→ Look for next greater, next smaller, span, or rectangle problems.

[10] Stack parsing

LC: 20, 71, 150, 224, 394, 735

→ Useful for expressions, nested structures, paths, and collision simulation.

[11] Queue and deque

LC: 239, 346, 362, 622, 641, 933

→ Use for rolling windows, ordered processing, and recent-event tracking.

[12] Intervals

LC: 56, 57, 252, 253, 435, 986

→ Sort by start or end time, then merge, count, or remove overlaps.

[13] Heap and top K

LC: 23, 215, 295, 347, 373, 973

→ Use when you repeatedly need the smallest, largest, or top K elements.

[14] Grid and graph BFS

LC: 127, 200, 286, 542, 752, 994

→ BFS is the default for shortest steps in an unweighted graph.

[15] Backtracking

LC: 39, 46, 78, 79, 90, 131

→ Choose, explore, undo. Use when all valid combinations must be generated.

[16] Tree DFS

LC: 98, 100, 104, 110, 124, 236

→ Decide what information each subtree should return to its parent.

[17] Tree BFS

LC: 102, 103, 199, 515, 637, 662

→ Use when the answer depends on levels, width, or visible nodes.

[18] Trie

LC: 208, 211, 212, 421, 648, 720

→ Use for prefixes, dictionaries, word search, and bitwise prefix matching.

[19] Union find

LC: 200, 261, 305, 547, 684, 721

→ Use for dynamic connectivity, grouping, and cycle detection.

[20] Topological sort

LC: 207, 210, 269, 310, 1136, 1203

→ Look for prerequisites, dependencies, ordering, or build sequences.

[21] Greedy

LC: 45, 55, 134, 435, 621, 763

→ Make the best local choice only when you can justify why it stays safe.

[22] One-dimensional DP

LC: 70, 139, 198, 213, 300, 322

→ Define the state clearly, then connect it to smaller states.

[23] Two-dimensional DP

LC: 62, 63, 64, 72, 221, 1143

→ Use when the state depends on two changing inputs or positions.

[24] Knapsack and subset DP

LC: 416, 474, 494, 518, 879, 1049

→ Look for choosing items under a limit, target, or capacity.

[25] Bit manipulation

LC: 136, 191, 231, 268, 338, 371

→ Learn XOR, masks, shifts, set-bit checks, and subset representation.

Do not solve these as 150 unrelated questions.

For every problem, write down:

→ Which pattern gave it away?

→ What changed from the standard version?

→ What would break the current solution?

→ Can you recognize the pattern within 90 seconds?

Any Clash of Clans players from Thoothukudi here? 👋

Vanakkam makkale! ❤️

We've created a Clash of Clans community called Tuty Official especially for Clashers from Thoothukudi.

The idea is simple:
• Meet local Clash players
• Share attacks and strategies
• Find clanmates
• Help each other during CWL and Clan Wars
• Build a stronger Thoothukudi Clash Community

If you're from Thoothukudi and play CoC, feel free to join the group and say hi.

Also curious—how many Clashers do we actually have in Thoothukudi? 😄

Vaa makka... Oru kai paathuralaam ❤️

If you're lazy like me.. Here is the Link 😅
https://link.clashofclans.com/?action=OpenGlobalChat&chatId=P01f99750fe074ef6b2c3f5daa4e0912f

Drop your TH level below 👇

Let's see if Tuty has any TH18's monsters hiding in this subreddit 😎

Vaa makka ❤️

Welcome

Hey Clashers,

We're looking for 2 active TH16+ players for the upcoming CWL.

Clan Name: GREAT WARiors
Clan Tag: #28URQLGLU
League: Master III
Open Spots: 2

If you're still looking for a CWL home, we'd be happy to have you join us. We're mainly looking for players who are active and can use their attacks during CWL.

You can either:
• Comment below
• Join directly using the clan tag

If you know a friend who's still searching for a clan, feel free to send them our way.

Hope to see you in Clashers ⚔️

Hey Clashers,

We're looking for 2 active TH16+ players for the upcoming CWL.

Clan Name: GREAT WARiors
Clan Tag: #28URQLGLU
League: Master III
Open Spots: 2

If you're still looking for a CWL home, we'd be happy to have you join us. We're mainly looking for players who are active and can use their attacks during CWL.

You can either:
• Comment below
• Join directly using the clan tag

If you know a friend who's still searching for a clan, feel free to send them our way.

Hope to see you in Clashers ⚔️

join here asap

Hey Clashers,

We're looking for 2 active TH16+ players for the upcoming CWL.

Clan Name: GREAT WARiors
Clan Tag: #28URQLGLU
League: Master III
Open Spots: 2

If you're still looking for a CWL home, we'd be happy to have you join us. We're mainly looking for players who are active and can use their attacks during CWL.

You can either:
• Comment below
• Join directly using the clan tag

If you know a friend who's still searching for a clan, feel free to send them our way.

Hope to see you in Clashers ⚔️

join here