Shubham Sourabhthe room · director's cutplain résumé

Room 04 · The Grind

The Grind 250 / 250

Interval training for the head: the full 250, solved twice, every solution machine-verified.

The Grind · NeetCode 250

250 of 250 problems chip-timed

every one chip-timed

18 categories · 4 solutions each

60 easy · 155 medium · 35 hard

250 classic algorithm problems. Each one solved twice — an honest brute force to learn the course, then the optimized line — in both Java and Python, with hints that nudge before they spoil, and a coach's board that walks the pattern step by step.

✓ CHIP-TIMEDEVERY PUBLISHED SOLUTION RAN GREEN IN CI · JDK 21 · CPYTHON 3.12

01Arrays & Hashing22 / 22
  1. 001Concatenation of ArrayEASY✓ CHIP-TIMED
  2. 002Contains DuplicateEASY✓ CHIP-TIMED
  3. 003Valid AnagramEASY✓ CHIP-TIMED
  4. 004Two SumEASY✓ CHIP-TIMED
  5. 005Longest Common PrefixEASY✓ CHIP-TIMED
  6. 006Group AnagramsMEDIUM✓ CHIP-TIMED
  7. 007Remove ElementEASY✓ CHIP-TIMED
  8. 008Majority ElementEASY✓ CHIP-TIMED
  9. 009Design HashSetEASY✓ CHIP-TIMED
  10. 010Design HashMapEASY✓ CHIP-TIMED
  11. 011Sort an ArrayMEDIUM✓ CHIP-TIMED
  12. 012Sort ColorsMEDIUM✓ CHIP-TIMED
  13. 013Top K Frequent ElementsMEDIUM✓ CHIP-TIMED
  14. 014Encode and Decode StringsMEDIUM✓ CHIP-TIMED
  15. 015Range Sum Query 2D ImmutableMEDIUM✓ CHIP-TIMED
  16. 016Product of Array Except SelfMEDIUM✓ CHIP-TIMED
  17. 017Valid SudokuMEDIUM✓ CHIP-TIMED
  18. 018Longest Consecutive SequenceMEDIUM✓ CHIP-TIMED
  19. 019Best Time to Buy And Sell Stock IIMEDIUM✓ CHIP-TIMED
  20. 020Majority Element IIMEDIUM✓ CHIP-TIMED
  21. 021Subarray Sum Equals KMEDIUM✓ CHIP-TIMED
  22. 022First Missing PositiveHARD✓ CHIP-TIMED
02Two Pointers13 / 13
  1. 023Reverse StringEASY✓ CHIP-TIMED
  2. 024Valid PalindromeEASY✓ CHIP-TIMED
  3. 025Valid Palindrome IIEASY✓ CHIP-TIMED
  4. 026Merge Strings AlternatelyEASY✓ CHIP-TIMED
  5. 027Merge Sorted ArrayEASY✓ CHIP-TIMED
  6. 028Remove Duplicates From Sorted ArrayEASY✓ CHIP-TIMED
  7. 029Two Sum II Input Array Is SortedMEDIUM✓ CHIP-TIMED
  8. 0303SumMEDIUM✓ CHIP-TIMED
  9. 0314SumMEDIUM✓ CHIP-TIMED
  10. 032Rotate ArrayMEDIUM✓ CHIP-TIMED
  11. 033Container With Most WaterMEDIUM✓ CHIP-TIMED
  12. 034Boats to Save PeopleMEDIUM✓ CHIP-TIMED
  13. 035Trapping Rain WaterHARD✓ CHIP-TIMED
03Sliding Window9 / 9
  1. 036Contains Duplicate IIEASY✓ CHIP-TIMED
  2. 037Best Time to Buy And Sell StockEASY✓ CHIP-TIMED
  3. 038Longest Substring Without Repeating CharactersMEDIUM✓ CHIP-TIMED
  4. 039Longest Repeating Character ReplacementMEDIUM✓ CHIP-TIMED
  5. 040Permutation In StringMEDIUM✓ CHIP-TIMED
  6. 041Minimum Size Subarray SumMEDIUM✓ CHIP-TIMED
  7. 042Find K Closest ElementsMEDIUM✓ CHIP-TIMED
  8. 043Minimum Window SubstringHARD✓ CHIP-TIMED
  9. 044Sliding Window MaximumHARD✓ CHIP-TIMED
04Stack15 / 15
  1. 045Baseball GameEASY✓ CHIP-TIMED
  2. 046Valid ParenthesesEASY✓ CHIP-TIMED
  3. 047Implement Stack Using QueuesEASY✓ CHIP-TIMED
  4. 048Implement Queue using StacksEASY✓ CHIP-TIMED
  5. 049Min StackMEDIUM✓ CHIP-TIMED
  6. 050Evaluate Reverse Polish NotationMEDIUM✓ CHIP-TIMED
  7. 051Generate ParenthesesMEDIUM✓ CHIP-TIMED
  8. 052Asteroid CollisionMEDIUM✓ CHIP-TIMED
  9. 053Daily TemperaturesMEDIUM✓ CHIP-TIMED
  10. 054Online Stock SpanMEDIUM✓ CHIP-TIMED
  11. 055Car FleetMEDIUM✓ CHIP-TIMED
  12. 056Simplify PathMEDIUM✓ CHIP-TIMED
  13. 057Decode StringMEDIUM✓ CHIP-TIMED
  14. 058Maximum Frequency StackHARD✓ CHIP-TIMED
  15. 059Largest Rectangle In HistogramHARD✓ CHIP-TIMED
06Linked List14 / 14
  1. 074Reverse Linked ListEASY✓ CHIP-TIMED
  2. 075Merge Two Sorted ListsEASY✓ CHIP-TIMED
  3. 076Linked List CycleEASY✓ CHIP-TIMED
  4. 077Reorder ListMEDIUM✓ CHIP-TIMED
  5. 078Remove Nth Node From End of ListMEDIUM✓ CHIP-TIMED
  6. 079Copy List With Random PointerMEDIUM✓ CHIP-TIMED
  7. 080Add Two NumbersMEDIUM✓ CHIP-TIMED
  8. 081Find The Duplicate NumberMEDIUM✓ CHIP-TIMED
  9. 082Reverse Linked List IIMEDIUM✓ CHIP-TIMED
  10. 083Design Circular QueueMEDIUM✓ CHIP-TIMED
  11. 084LRU CacheMEDIUM✓ CHIP-TIMED
  12. 085LFU CacheHARD✓ CHIP-TIMED
  13. 086Merge K Sorted ListsHARD✓ CHIP-TIMED
  14. 087Reverse Nodes In K GroupHARD✓ CHIP-TIMED
07Trees23 / 23
  1. 088Binary Tree Inorder TraversalEASY✓ CHIP-TIMED
  2. 089Binary Tree Preorder TraversalEASY✓ CHIP-TIMED
  3. 090Binary Tree Postorder TraversalEASY✓ CHIP-TIMED
  4. 091Invert Binary TreeEASY✓ CHIP-TIMED
  5. 092Maximum Depth of Binary TreeEASY✓ CHIP-TIMED
  6. 093Diameter of Binary TreeEASY✓ CHIP-TIMED
  7. 094Balanced Binary TreeEASY✓ CHIP-TIMED
  8. 095Same TreeEASY✓ CHIP-TIMED
  9. 096Subtree of Another TreeEASY✓ CHIP-TIMED
  10. 097Lowest Common Ancestor of a Binary Search TreeMEDIUM✓ CHIP-TIMED
  11. 098Insert into a Binary Search TreeMEDIUM✓ CHIP-TIMED
  12. 099Delete Node in a BSTMEDIUM✓ CHIP-TIMED
  13. 100Binary Tree Level Order TraversalMEDIUM✓ CHIP-TIMED
  14. 101Binary Tree Right Side ViewMEDIUM✓ CHIP-TIMED
  15. 102Construct Quad TreeMEDIUM✓ CHIP-TIMED
  16. 103Count Good Nodes In Binary TreeMEDIUM✓ CHIP-TIMED
  17. 104Validate Binary Search TreeMEDIUM✓ CHIP-TIMED
  18. 105Kth Smallest Element In a BstMEDIUM✓ CHIP-TIMED
  19. 106Construct Binary Tree From Preorder And Inorder TraversalMEDIUM✓ CHIP-TIMED
  20. 107House Robber IIIMEDIUM✓ CHIP-TIMED
  21. 108Delete Leaves With a Given ValueMEDIUM✓ CHIP-TIMED
  22. 109Binary Tree Maximum Path SumHARD✓ CHIP-TIMED
  23. 110Serialize And Deserialize Binary TreeHARD✓ CHIP-TIMED
08Heap / Priority Queue12 / 12
  1. 111Kth Largest Element In a StreamEASY✓ CHIP-TIMED
  2. 112Last Stone WeightEASY✓ CHIP-TIMED
  3. 113K Closest Points to OriginMEDIUM✓ CHIP-TIMED
  4. 114Kth Largest Element In An ArrayMEDIUM✓ CHIP-TIMED
  5. 115Task SchedulerMEDIUM✓ CHIP-TIMED
  6. 116Design TwitterMEDIUM✓ CHIP-TIMED
  7. 117Single Threaded CPUMEDIUM✓ CHIP-TIMED
  8. 118Reorganize StringMEDIUM✓ CHIP-TIMED
  9. 119Longest Happy StringMEDIUM✓ CHIP-TIMED
  10. 120Car PoolingMEDIUM✓ CHIP-TIMED
  11. 121Find Median From Data StreamHARD✓ CHIP-TIMED
  12. 122IPOHARD✓ CHIP-TIMED
09Backtracking16 / 16
  1. 123Sum of All Subsets XOR TotalEASY✓ CHIP-TIMED
  2. 124SubsetsMEDIUM✓ CHIP-TIMED
  3. 125Combination SumMEDIUM✓ CHIP-TIMED
  4. 126Combination Sum IIMEDIUM✓ CHIP-TIMED
  5. 127CombinationsMEDIUM✓ CHIP-TIMED
  6. 128PermutationsMEDIUM✓ CHIP-TIMED
  7. 129Subsets IIMEDIUM✓ CHIP-TIMED
  8. 130Permutations IIMEDIUM✓ CHIP-TIMED
  9. 131Word SearchMEDIUM✓ CHIP-TIMED
  10. 132Palindrome PartitioningMEDIUM✓ CHIP-TIMED
  11. 133Letter Combinations of a Phone NumberMEDIUM✓ CHIP-TIMED
  12. 134Matchsticks to SquareMEDIUM✓ CHIP-TIMED
  13. 135Partition to K Equal Sum SubsetsMEDIUM✓ CHIP-TIMED
  14. 136N QueensHARD✓ CHIP-TIMED
  15. 137N Queens IIHARD✓ CHIP-TIMED
  16. 138Word Break IIHARD✓ CHIP-TIMED
10Tries4 / 4
  1. 139Implement Trie Prefix TreeMEDIUM✓ CHIP-TIMED
  2. 140Design Add And Search Words Data StructureMEDIUM✓ CHIP-TIMED
  3. 141Extra Characters in a StringMEDIUM✓ CHIP-TIMED
  4. 142Word Search IIHARD✓ CHIP-TIMED
11Graphs21 / 21
  1. 143Island PerimeterEASY✓ CHIP-TIMED
  2. 144Verifying An Alien DictionaryEASY✓ CHIP-TIMED
  3. 145Find the Town JudgeEASY✓ CHIP-TIMED
  4. 146Number of IslandsMEDIUM✓ CHIP-TIMED
  5. 147Max Area of IslandMEDIUM✓ CHIP-TIMED
  6. 148Clone GraphMEDIUM✓ CHIP-TIMED
  7. 149Walls And GatesMEDIUM✓ CHIP-TIMED
  8. 150Rotting OrangesMEDIUM✓ CHIP-TIMED
  9. 151Pacific Atlantic Water FlowMEDIUM✓ CHIP-TIMED
  10. 152Surrounded RegionsMEDIUM✓ CHIP-TIMED
  11. 153Open The LockMEDIUM✓ CHIP-TIMED
  12. 154Course ScheduleMEDIUM✓ CHIP-TIMED
  13. 155Course Schedule IIMEDIUM✓ CHIP-TIMED
  14. 156Graph Valid TreeMEDIUM✓ CHIP-TIMED
  15. 157Course Schedule IVMEDIUM✓ CHIP-TIMED
  16. 158Number of Connected Components In An Undirected GraphMEDIUM✓ CHIP-TIMED
  17. 159Redundant ConnectionMEDIUM✓ CHIP-TIMED
  18. 160Accounts MergeMEDIUM✓ CHIP-TIMED
  19. 161Evaluate DivisionMEDIUM✓ CHIP-TIMED
  20. 162Minimum Height TreesMEDIUM✓ CHIP-TIMED
  21. 163Word LadderHARD✓ CHIP-TIMED
12Advanced Graphs10 / 10
  1. 164Path with Minimum EffortMEDIUM✓ CHIP-TIMED
  2. 165Network Delay TimeMEDIUM✓ CHIP-TIMED
  3. 166Reconstruct ItineraryHARD✓ CHIP-TIMED
  4. 167Min Cost to Connect All PointsMEDIUM✓ CHIP-TIMED
  5. 168Swim In Rising WaterHARD✓ CHIP-TIMED
  6. 169Alien DictionaryHARD✓ CHIP-TIMED
  7. 170Cheapest Flights Within K StopsMEDIUM✓ CHIP-TIMED
  8. 171Find Critical and Pseudo Critical Edges in Minimum Spanning TreeHARD✓ CHIP-TIMED
  9. 172Build a Matrix With ConditionsHARD✓ CHIP-TIMED
  10. 173Greatest Common Divisor TraversalHARD✓ CHIP-TIMED
131-D Dynamic Programming17 / 17
  1. 174Climbing StairsEASY✓ CHIP-TIMED
  2. 175Min Cost Climbing StairsEASY✓ CHIP-TIMED
  3. 176N-th Tribonacci NumberEASY✓ CHIP-TIMED
  4. 177House RobberMEDIUM✓ CHIP-TIMED
  5. 178House Robber IIMEDIUM✓ CHIP-TIMED
  6. 179Longest Palindromic SubstringMEDIUM✓ CHIP-TIMED
  7. 180Palindromic SubstringsMEDIUM✓ CHIP-TIMED
  8. 181Decode WaysMEDIUM✓ CHIP-TIMED
  9. 182Coin ChangeMEDIUM✓ CHIP-TIMED
  10. 183Maximum Product SubarrayMEDIUM✓ CHIP-TIMED
  11. 184Word BreakMEDIUM✓ CHIP-TIMED
  12. 185Longest Increasing SubsequenceMEDIUM✓ CHIP-TIMED
  13. 186Partition Equal Subset SumMEDIUM✓ CHIP-TIMED
  14. 187Combination Sum IVMEDIUM✓ CHIP-TIMED
  15. 188Perfect SquaresMEDIUM✓ CHIP-TIMED
  16. 189Integer BreakMEDIUM✓ CHIP-TIMED
  17. 190Stone Game IIIHARD✓ CHIP-TIMED
142-D Dynamic Programming16 / 16
  1. 191Unique PathsMEDIUM✓ CHIP-TIMED
  2. 192Unique Paths IIMEDIUM✓ CHIP-TIMED
  3. 193Minimum Path SumMEDIUM✓ CHIP-TIMED
  4. 194Longest Common SubsequenceMEDIUM✓ CHIP-TIMED
  5. 195Last Stone Weight IIMEDIUM✓ CHIP-TIMED
  6. 196Best Time to Buy And Sell Stock With CooldownMEDIUM✓ CHIP-TIMED
  7. 197Coin Change IIMEDIUM✓ CHIP-TIMED
  8. 198Target SumMEDIUM✓ CHIP-TIMED
  9. 199Interleaving StringMEDIUM✓ CHIP-TIMED
  10. 200Stone GameMEDIUM✓ CHIP-TIMED
  11. 201Stone Game IIMEDIUM✓ CHIP-TIMED
  12. 202Longest Increasing Path In a MatrixHARD✓ CHIP-TIMED
  13. 203Distinct SubsequencesHARD✓ CHIP-TIMED
  14. 204Edit DistanceMEDIUM✓ CHIP-TIMED
  15. 205Burst BalloonsHARD✓ CHIP-TIMED
  16. 206Regular Expression MatchingHARD✓ CHIP-TIMED
15Greedy14 / 14
  1. 207Lemonade ChangeEASY✓ CHIP-TIMED
  2. 208Maximum SubarrayMEDIUM✓ CHIP-TIMED
  3. 209Maximum Sum Circular SubarrayMEDIUM✓ CHIP-TIMED
  4. 210Longest Turbulent SubarrayMEDIUM✓ CHIP-TIMED
  5. 211Jump GameMEDIUM✓ CHIP-TIMED
  6. 212Jump Game IIMEDIUM✓ CHIP-TIMED
  7. 213Jump Game VIIMEDIUM✓ CHIP-TIMED
  8. 214Gas StationMEDIUM✓ CHIP-TIMED
  9. 215Hand of StraightsMEDIUM✓ CHIP-TIMED
  10. 216Dota2 SenateMEDIUM✓ CHIP-TIMED
  11. 217Merge Triplets to Form Target TripletMEDIUM✓ CHIP-TIMED
  12. 218Partition LabelsMEDIUM✓ CHIP-TIMED
  13. 219Valid Parenthesis StringMEDIUM✓ CHIP-TIMED
  14. 220CandyHARD✓ CHIP-TIMED
16Intervals7 / 7
  1. 221Insert IntervalMEDIUM✓ CHIP-TIMED
  2. 222Merge IntervalsMEDIUM✓ CHIP-TIMED
  3. 223Non Overlapping IntervalsMEDIUM✓ CHIP-TIMED
  4. 224Meeting RoomsEASY✓ CHIP-TIMED
  5. 225Meeting Rooms IIMEDIUM✓ CHIP-TIMED
  6. 226Meeting Rooms IIIHARD✓ CHIP-TIMED
  7. 227Minimum Interval to Include Each QueryHARD✓ CHIP-TIMED
17Math & Geometry13 / 13
  1. 228Excel Sheet Column TitleEASY✓ CHIP-TIMED
  2. 229Greatest Common Divisor of StringsEASY✓ CHIP-TIMED
  3. 230Insert Greatest Common Divisors in Linked ListMEDIUM✓ CHIP-TIMED
  4. 231Transpose MatrixEASY✓ CHIP-TIMED
  5. 232Rotate ImageMEDIUM✓ CHIP-TIMED
  6. 233Spiral MatrixMEDIUM✓ CHIP-TIMED
  7. 234Set Matrix ZeroesMEDIUM✓ CHIP-TIMED
  8. 235Happy NumberEASY✓ CHIP-TIMED
  9. 236Plus OneEASY✓ CHIP-TIMED
  10. 237Roman to IntegerEASY✓ CHIP-TIMED
  11. 238Pow(x, n)MEDIUM✓ CHIP-TIMED
  12. 239Multiply StringsMEDIUM✓ CHIP-TIMED
  13. 240Detect SquaresMEDIUM✓ CHIP-TIMED
18Bit Manipulation10 / 10
  1. 241Single NumberEASY✓ CHIP-TIMED
  2. 242Number of 1 BitsEASY✓ CHIP-TIMED
  3. 243Counting BitsEASY✓ CHIP-TIMED
  4. 244Add BinaryEASY✓ CHIP-TIMED
  5. 245Reverse BitsEASY✓ CHIP-TIMED
  6. 246Missing NumberEASY✓ CHIP-TIMED
  7. 247Sum of Two IntegersMEDIUM✓ CHIP-TIMED
  8. 248Reverse IntegerMEDIUM✓ CHIP-TIMED
  9. 249Bitwise AND of Numbers RangeMEDIUM✓ CHIP-TIMED
  10. 250Minimum Array EndMEDIUM✓ CHIP-TIMED