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Software Development Engineer, Senior SDE, Full-Stack Developer at Google, Meta, Amazon, Apple, Netflix, Microsoft, Uber, Airbnb, LinkedIn, Flipkart, Swiggy, Zomato, PhonePe, Razorpay, Cred, Zerodha, Atlassian, Salesforce, Adobe, Oracle. Expected CTC: 12-50 LPA for entry roles; 25-95 LPA for SDE-2 and above.
📚 Curriculum (10 Units)
Unit 1: Array & Matrix Problems (10 Questions) 10 topics
P1. Two Sum (Easy) — Amazon, Google
Return indices of two numbers that add up to target. Brute O(n²) → HashMap O(n). Follow-ups: sorted variant with two-pointer, multiple pairs, 3Sum extension.
P2. Best Time to Buy and Sell Stock (Easy) — Amazon, Meta
Max profit with one transaction. Track min-so-far in single pass. Variants: unlimited transactions, at most 2, with cooldown, with fee.
P3. Maximum Subarray (Kadane) (Medium) — Amazon, LinkedIn
Find contiguous subarray with largest sum. Kadane's O(n). Follow-up: return the subarray itself, circular variant, max product subarray.
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P4. Product of Array Except Self (Medium) — Amazon, Apple
Without division, compute product of all except self. Left-pass and right-pass arrays, then O(1) extra space optimization.
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P5. Trapping Rain Water (Hard) — Google, Amazon
Compute trapped water. Three approaches: DP arrays O(n)/O(n), two-pointer O(n)/O(1), monotonic stack.
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P6. Rotate Image (Medium) — Microsoft, Apple
Rotate n×n matrix 90° clockwise in place. Transpose + row reverse. Handle rectangular variant separately.
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P7. Spiral Matrix (Medium) — Google, Uber
Return matrix elements in spiral order. Four boundaries approach, direction-vector approach. Follow-up: generate spiral from n.
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P8. Set Matrix Zeroes (Medium) — Meta, Microsoft
If element is 0, set its row and column to 0. Naive O(m+n) markers → O(1) using first row/column as markers.
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P9. Search in Rotated Sorted Array (Medium) — Amazon, Meta
Modified binary search. Identify sorted half, decide which half target lies in. Handle duplicates variant (II).
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P10. Median of Two Sorted Arrays (Hard) — Google, Adobe
O(log(min(n,m))) binary search on partition. Most-asked hard problem. Walkthrough with visualization.
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Unit 2: String Manipulation Problems (10 Questions) 10 topics
P11. Longest Substring Without Repeating Characters (Medium) — Amazon, Meta
Sliding window with HashSet or HashMap for jump optimization. O(n) time.
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P12. Longest Palindromic Substring (Medium) — Amazon, Microsoft
Expand-around-center O(n²) / O(1). Manacher's O(n) as bonus. DP approach as alternative.
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P13. Valid Anagram (Easy) — Amazon, Google
Frequency array or sorting. Unicode variant with HashMap. Follow-up: group anagrams.
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P14. Group Anagrams (Medium) — Amazon, Uber
HashMap with sorted-string key or character-count tuple key. O(NK log K) vs O(NK).
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P15. Valid Parentheses (Easy) — Google, Meta
Stack-based matching. Extensions: minimum insertions to make valid, longest valid parentheses.
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P16. Minimum Window Substring (Hard) — Amazon, LinkedIn
Sliding window with need-count HashMap. Classic hard string problem. Template for all "window with condition" problems.
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P17. String to Integer (atoi) (Medium) — Meta, Google
Edge cases galore: whitespace, +/-, overflow, non-digits. Why Meta loves this problem.
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P18. Implement strStr / KMP (Medium) — Google, Amazon
Naive O(nm), KMP O(n+m), Rabin-Karp with rolling hash. Choose based on constraints.
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P19. Word Break (Medium) — Amazon, Meta
DP with dictionary lookup. Top-down memoized recursion. Follow-up: Word Break II (return all sentences).
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P20. Regular Expression Matching (Hard) — Meta, Google
2D DP with "." and "*". One of the trickiest string DP problems. State transition walkthrough.
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Unit 3: Linked List Problems (10 Questions) 10 topics
P21. Reverse Linked List (Easy) — Amazon, Meta
Iterative with 3 pointers and recursive. Foundation for many list problems.
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P22. Merge Two Sorted Lists (Easy) — Amazon, Apple
Dummy node pattern. Iterative and recursive. Follow-up: merge K sorted lists.
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P23. Linked List Cycle I & II (Easy/Medium) — Amazon, Microsoft
Floyd's tortoise-hare for detection, then find cycle start with mathematical proof.
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P24. Remove Nth Node From End (Medium) — Meta, Google
Two pointers with N-gap, one pass. Why dummy node simplifies edge cases.
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P25. Add Two Numbers (Medium) — Amazon, Apple
Digit-by-digit with carry. Handle unequal lengths. Forward-order variant (II) uses stacks.
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P26. Copy List with Random Pointer (Medium) — Meta, Amazon
HashMap O(n) space → O(1) interleaving trick. Google favorite.
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P27. Merge K Sorted Lists (Hard) — Amazon, Google
Min-heap O(N log K) vs divide-and-conquer merge O(N log K). Both optimal but different constants.
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P28. Reverse Nodes in k-Group (Hard) — Microsoft, Google
Reverse every k nodes; leave remaining. Dummy node + careful pointer tracking.
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P29. LRU Cache (Medium) — Amazon, Meta
HashMap + Doubly LinkedList for O(1) get/put. One of the top-3 most-asked design problems.
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P30. LFU Cache (Hard) — Amazon, Google
HashMap + HashMap + minFreq pointer. Harder than LRU, tests data-structure design.
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Unit 4: Stack, Queue & Hashing Problems (10 Questions) 10 topics
P31. Min Stack (Medium) — Amazon, Google
getMin in O(1). Two-stack approach or storing (val, currentMin) pairs.
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P32. Next Greater Element I & II (Medium) — Amazon, Bloomberg
Monotonic decreasing stack. II handles circular arrays with index modulo.
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P33. Daily Temperatures (Medium) — Meta, Amazon
Days until warmer temperature. Monotonic stack storing indices.
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P34. Largest Rectangle in Histogram (Hard) — Amazon, Google
Monotonic increasing stack, compute area on pop. Setup for Maximal Rectangle.
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P35. Maximal Rectangle (Hard) — Meta, Google
Reduce to Largest Rectangle on each row using histogram heights. O(mn).
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P36. Sliding Window Maximum (Hard) — Amazon, Google
Monotonic deque storing indices. O(n) time. Common pattern for "window max/min".
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P37. Top K Frequent Elements (Medium) — Amazon, Meta
HashMap + min-heap of size K, or bucket sort by frequency for O(n).
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P38. Longest Consecutive Sequence (Medium) — Google, Amazon
HashSet with "start of sequence" check. O(n) overall despite inner loop.
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P39. Subarray Sum Equals K (Medium) — Meta, Amazon
Prefix sum + HashMap of sum frequencies. Handles negatives (unlike sliding window).
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P40. Basic Calculator II (Medium) — Meta, Google
Handle +, -, *, / with precedence using stack. Basic Calculator I uses parentheses recursion.
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Unit 5: Tree & BST Problems (10 Questions) 10 topics
P41. Maximum Depth of Binary Tree (Easy) — Amazon, LinkedIn
DFS recursion or BFS level count. Warm-up for all tree problems.
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P42. Invert Binary Tree (Easy) — Google
Swap left/right recursively. The famous problem that rejected Max Howell from Google.
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P43. Validate Binary Search Tree (Medium) — Amazon, Meta
Range (min, max) pass-down or inorder must be strictly increasing. Common bug: using
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P44. Binary Tree Level Order Traversal (Medium) — Amazon, Meta
BFS with queue. Zigzag variant, bottom-up variant, right-side view.
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P45. Lowest Common Ancestor of Binary Tree (Medium) — Meta, Amazon
Post-order return pattern: return node if it matches p or q, or LCA found in subtree.
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P46. Binary Tree Maximum Path Sum (Hard) — Meta, Amazon
DFS returning max gain, tracking global max including "through-node" sums.
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P47. Serialize and Deserialize Binary Tree (Hard) — Meta, LinkedIn
Preorder with null markers or level-order with delimiters. Must round-trip.
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P48. Construct Binary Tree from Preorder + Inorder (Medium) — Amazon, Microsoft
Recursive split using HashMap for inorder indices. O(n).
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P49. Kth Smallest Element in BST (Medium) — Amazon, Uber
Inorder traversal with counter, or iterative stack-based early termination.
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P50. Flatten Binary Tree to Linked List (Medium) — Meta, Microsoft
In-place preorder flatten. O(1) extra space variant using right-child threading.
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Unit 6: Graph Problems (10 Questions) 10 topics
P51. Number of Islands (Medium) — Amazon, Meta
DFS/BFS flood fill on 2D grid. Union-Find alternative. Follow-up: 3D islands.
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P52. Clone Graph (Medium) — Meta, Amazon
DFS/BFS with HashMap. Handle cycles correctly.
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P53. Course Schedule I & II (Medium) — Amazon, Meta
Topological sort via Kahn's (BFS with in-degree) or DFS with cycle detection.
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P54. Word Ladder (Hard) — Amazon, Google
BFS on word graph. Bidirectional BFS optimization. Word Ladder II returns all shortest paths.
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P55. Pacific Atlantic Water Flow (Medium) — Google, Amazon
Reverse BFS/DFS from both oceans, find intersection. Smarter than forward simulation.
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P56. Rotting Oranges (Medium) — Amazon, Google
Multi-source BFS. Track time as BFS level. Return -1 if unreachable fresh orange exists.
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P57. Network Delay Time (Medium) — Google, Amazon
Dijkstra's with min-heap. Return max distance or -1 if any unreachable.
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P58. Cheapest Flights Within K Stops (Medium) — Amazon, Meta
Modified BFS with stop-count, or Bellman-Ford variant. Dijkstra needs state augmentation.
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P59. Alien Dictionary (Hard) — Meta, Google
Build character graph from adjacent word pairs, topological sort. Edge case: prefix violation.
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P60. Critical Connections in a Network (Hard) — Meta, Amazon
Tarjan's bridge-finding with DFS low-link values. Classic hard graph problem.
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Unit 7: Dynamic Programming Problems (10 Questions) 10 topics
P61. Climbing Stairs (Easy) — Amazon, Adobe
Fibonacci-equivalent. O(1) space with two variables. Follow-up: min cost variant.
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P62. House Robber I, II & III (Medium) — Amazon, LinkedIn
Linear array → circular → binary tree. Same recurrence, different traversal.
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P63. Coin Change (Medium) — Amazon, Meta
Unbounded knapsack. Min coins (I) and number of ways (II) are different recurrences.
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P64. Longest Increasing Subsequence (Medium) — Amazon, Google
O(n²) DP → O(n log n) with patience sort + binary search.
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P65. Longest Common Subsequence (Medium) — Amazon, Apple
Classic 2D DP. Variants: longest common substring, shortest common supersequence.
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P66. Edit Distance (Hard) — Amazon, Google
Levenshtein distance 2D DP. O(nm). Space-optimize to O(min(n, m)).
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P67. Unique Paths I & II (Medium) — Amazon, Meta
Grid DP. II adds obstacles. Math shortcut: C(m+n-2, m-1) for I.
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P68. Word Break II (Hard) — Google, Meta
Return all valid sentence segmentations. Memoized recursion with HashMap.
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P69. Decode Ways (Medium) — Meta, Amazon
Map 1-26 to A-Z. Carefully handle '0'. Similar to climbing stairs with constraints.
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P70. Best Time to Buy/Sell Stock with Cooldown (Medium) — Google, Amazon
State machine DP: held, sold, reset. Three states, three transitions.
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Unit 8: Heap & Priority Queue Problems (10 Questions) 10 topics
P71. Kth Largest Element in an Array (Medium) — Amazon, Meta
Min-heap of size K O(n log K), or Quickselect average O(n).
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P72. Find Median from Data Stream (Hard) — Amazon, Google
Max-heap (lower half) + Min-heap (upper half). Balance invariant after each insert.
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P73. K Closest Points to Origin (Medium) — Meta, Amazon
Max-heap of size K by distance², or Quickselect on distance.
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P74. Top K Frequent Words (Medium) — Amazon, Meta
Heap with custom comparator: frequency desc, then lexicographic asc.
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P75. Reorganize String (Medium) — Google, Amazon
Max-heap by frequency, place most frequent with gap. Infeasible if max freq > (n+1)/2.
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P76. Task Scheduler (Medium) — Meta, Amazon
Max-heap greedy simulation, or math formula: max((maxCount-1)*(n+1) + maxCountFreq, len).
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P77. Meeting Rooms II (Medium) — Meta, Google
Min-heap of end times, or sort-and-sweep with two sorted arrays. Classic interval problem.
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P78. Merge K Sorted Arrays (Medium) — LinkedIn, Amazon
Min-heap with (value, array index, element index) tuples. O(N log K).
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P79. Find K Pairs with Smallest Sums (Medium) — Amazon, Google
Min-heap BFS over pair space. Avoid revisiting with visited set.
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P80. IPO / Maximize Capital (Hard) — Google, Amazon
Two heaps: min-heap on capital (available projects), max-heap on profit (pickable).
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Unit 9: Backtracking & Greedy Problems (10 Questions) 10 topics
P81. Subsets (Medium) — Meta, Amazon
Backtracking template: include/exclude. Iterative bit-mask variant. Subsets II handles duplicates.
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P82. Permutations (Medium) — Meta, Google
Backtrack with used[] flag. Permutations II: sort + skip duplicates.
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P83. Combination Sum I & II (Medium) — Amazon, Meta
I allows unlimited reuse; II each element once. Skip duplicates correctly.
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P84. N-Queens (Hard) — Amazon, Apple
Backtrack column-by-column. Track diagonals with HashSet or bitmask. Count-only version for II.
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P85. Word Search I & II (Medium/Hard) — Amazon, Microsoft
II uses Trie + DFS with pruning — standard hard interview pattern.
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P86. Sudoku Solver (Hard) — Google, Uber
Backtracking with row/col/box bitsets for O(1) constraint check.
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P87. Jump Game I & II (Medium) — Amazon, Meta
Greedy farthest-reach for I. II uses BFS-like greedy for min jumps.
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P88. Gas Station (Medium) — Amazon, Google
Greedy: if total gas ≥ total cost, answer exists. Find start by resetting on deficit.
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P89. Partition Labels (Medium) — Amazon, Google
Greedy: last occurrence map, extend partition end until i == end.
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P90. Merge Intervals (Medium) — Meta, Amazon
Sort by start, merge overlapping. Extensions: insert interval, meeting rooms, employee free time.
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Unit 10: Hard Interview Problems & Mock Round (10 Questions) 10 topics
P91. Trapping Rain Water II (3D) (Hard) — Google, Amazon
2D heightmap version. Min-heap from boundary, BFS inward raising water levels.
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P92. Longest Valid Parentheses (Hard) — Meta, Amazon
Stack storing last invalid index, or two-pass counting. DP is a third approach.
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P93. Sliding Puzzle (Hard) — Amazon, Meta
BFS on board states as strings. Target state reachability check.
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P94. Shortest Path in a Grid with Obstacles Elimination (Hard) — Meta
BFS with state (row, col, remainingEliminations).
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P95. Count of Smaller Numbers After Self (Hard) — Google, Amazon
Merge sort with index tracking, or Binary Indexed Tree (Fenwick).
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P96. Recover Binary Search Tree (Medium/Hard) — Meta, Amazon
Inorder traversal to find two swapped nodes. Morris traversal for O(1) space.
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P97. Smallest Range Covering Elements from K Lists (Hard) — Amazon, Google
Min-heap + track max, slide range. Similar to merge K sorted.
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P98. Design Twitter (Medium/Hard) — Meta, Twitter
HashMap + follow set + heap-merge recent tweets. Design pattern.
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P99. Text Justification (Hard) — LinkedIn, Google
Greedy line-packing + careful spacing distribution (extra spaces on left).
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P100. Mock Interview Round + Resume & Offer Negotiation
Full 45-min mock with interviewer rubric, common rejection reasons, compensation negotiation scripts for 2026.
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90 Days
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