50 Days Plan

Day 1 (2025-12-30) — Sliding Window baseline + 1 Prefix/Hash

• LC1343 — Count Subarrays of Size K with Average Greater than or Equal to Threshold | Sliding Window | Easy | Companies: Amazon
• LC424 — Longest Repeating Character Replacement | Sliding Window | Medium | Companies: Google; Meta (Facebook); Microsoft
• LC159 — Longest Substring with At Most Two Distinct Characters | Sliding Window | Medium | Companies: Bloomberg; Google
• LC1456 — Maximum Number of Vowels in a Substring of Given Length | Sliding Window | Medium | Companies: Amazon; Google
• LC644 — Maximum Average Subarray II | Sliding Window | Hard | Companies: Google; Meta (Facebook)
• LC128 — Longest Consecutive Sequence | Hashing/Prefix | Medium | Companies: Amazon; Google; Meta

Day 2 (2025-12-31) — Sliding Window advanced

• LC3 — Longest Substring Without Repeating Characters | Sliding Window | Medium | Companies: Adobe; Amazon; Bloomberg; Google; Microsoft
• LC1004 — Max Consecutive Ones III | Sliding Window | Medium | Companies: Amazon; Google
• LC904 — Fruits Into Baskets | Sliding Window | Medium | Companies: Amazon; Google; Uber
• LC2024 — Maximize the Confusion of an Exam | Sliding Window | Medium | Companies: Amazon; Google; Meta (Facebook)
• LC76 — Minimum Window Substring | Sliding Window | Hard | Companies: Amazon; Google; Meta (Facebook); Microsoft
• LC992 — Subarrays with K Different Integers | Sliding Window | Hard | Companies: Google; Meta (Facebook)

Day 3 (2025-01-1) — Hashing/Prefix baseline

• LC1 — Two Sum | Hashing/Prefix | Easy | Companies: Amazon; Google; Meta; Microsoft
• LC49 — Group Anagrams | Hashing/Prefix | Medium | Companies: Amazon; Bloomberg; Google; Meta; Microsoft
• LC560 — Subarray Sum Equals K | Hashing/Prefix | Medium | Companies: Amazon; Google; Meta (Facebook)
• LC347 — Top K Frequent Elements | Hashing/Prefix | Medium | Companies: Amazon; Microsoft
• LC525 — Contiguous Array | Hashing/Prefix | Medium | Companies: Amazon; Facebook; Google
• LC149 — Max Points on a Line | Hashing/Prefix | Hard | Companies: Amazon; Google; Microsoft

Day 4 (2025-01-2) — Hashing/Prefix advanced

• LC36 — Valid Sudoku | Hashing/Prefix | Medium | Companies: Amazon; Apple; Google; Meta; Microsoft
• LC438 — Find All Anagrams in a String | Hashing/Prefix | Medium | Companies: Amazon; Microsoft
• LC299 — Bulls and Cows | Hashing/Prefix | Medium | Companies: Google
• LC523 — Continuous Subarray Sum | Hashing/Prefix | Medium | Companies: Amazon; Google; Microsoft
• LC41 — First Missing Positive | Hashing/Prefix | Hard | Companies: Amazon; Microsoft
• LC30 — Substring with Concatenation of All Words | Hashing/Prefix | Hard | Companies: Amazon; Facebook; Google; Microsoft

Day 5 (2025-01-3) — Two Pointers baseline

• LC125 — Valid Palindrome | Two Pointers | Easy | Companies: Amazon; Facebook; Microsoft; Uber
• LC15 — 3Sum | Two Pointers | Medium | Companies: Amazon; Bloomberg; Meta; Microsoft
• LC11 — Container With Most Water | Two Pointers | Medium | Companies: Amazon; Bloomberg; Google; Meta; Microsoft
• LC80 — Remove Duplicates from Sorted Array II | Two Pointers | Medium | Companies: Amazon; Microsoft
• LC713 — Subarray Product Less Than K | Two Pointers | Medium | Companies: Amazon; Google; Meta
• LC881 — Boats to Save People | Two Pointers | Medium | Companies: Amazon; Google

Day 6 (2025-01-4) — Stack baseline

• LC20 — Valid Parentheses | Stack | Easy | Companies: Amazon; Google; Microsoft; Meta
• LC71 — Simplify Path | Stack | Medium | Companies: Amazon; Google; Microsoft
• LC150 — Evaluate Reverse Polish Notation | Stack | Medium | Companies: Amazon; Google; LinkedIn
• LC739 — Daily Temperatures | Stack | Medium | Companies: Amazon; Google
• LC84 — Largest Rectangle in Histogram | Stack | Hard | Companies: Amazon; Google; Microsoft
• LC32 — Longest Valid Parentheses | Stack | Hard | Companies: Amazon; Google; Meta; Microsoft

Day 7 (2025-01-5) — REVISION: 3 new (2H+1M)

• LC10 — Regular Expression Matching | DP | Hard | Companies: Amazon; Google; Meta
• LC42 — Trapping Rain Water | Stack | Hard | Companies: Amazon; Google; Meta; Microsoft
• LC221 — Maximal Square | DP | Medium | Companies: Amazon; Google; Microsoft

Day 8 (2025-01-6) — Binary Search baseline

• LC35 — Search Insert Position | Binary Search | Easy | Companies: Amazon; Google
• LC153 — Find Minimum in Rotated Sorted Array | Binary Search | Medium | Companies: Amazon; Bloomberg; Google; Microsoft
• LC33 — Search in Rotated Sorted Array | Binary Search | Medium | Companies: Amazon; Google; Microsoft
• LC162 — Find Peak Element | Binary Search | Medium | Companies: Amazon; Google; Microsoft
• LC34 — Find First and Last Position of Element in Sorted Array | Binary Search | Medium | Companies: Amazon; LinkedIn; Microsoft
• LC4 — Median of Two Sorted Arrays | Binary Search | Hard | Companies: Amazon; Google; Microsoft

Day 9 (2026-01-7) — Heap patterns

• LC215 — Kth Largest Element in an Array | Heap | Medium | Companies: Amazon; Facebook; Google; Microsoft
• LC347 — Top K Frequent Elements | Hashing/Prefix | Medium | Companies: Amazon; Microsoft
• LC973 — K Closest Points to Origin | Heap | Medium | Companies: Amazon; Google
• LC295 — Find Median from Data Stream | Heap | Hard | Companies: Amazon; Google; Microsoft
• LC692 — Top K Frequent Words | Heap | Medium | Companies: Amazon; Google; Microsoft
• LC621 — Task Scheduler | Heap | Medium | Companies: Amazon; Google; Microsoft

Day 10 (2026-01-08) — Intervals + sweep line

• LC56 — Merge Intervals | Intervals | Medium | Companies: Amazon; Facebook; Google; Microsoft
• LC57 — Insert Interval | Intervals | Medium | Companies: Amazon; Facebook; Google
• LC252 — Meeting Rooms | Intervals | Easy | Companies: Amazon; Facebook; Google
• LC253 — Meeting Rooms II | Intervals | Medium | Companies: Amazon; Facebook; Google; Microsoft
• LC435 — Non-overlapping Intervals | Intervals | Medium | Companies: Amazon; Google
• LC218 — The Skyline Problem | Intervals | Hard | Companies: Amazon; Google; Microsoft

Day 11 (2026-01-09) — Tree baseline

• LC104 — Maximum Depth of Binary Tree | Tree | Easy | Companies: Amazon; Google; Microsoft
• LC102 — Binary Tree Level Order Traversal | Tree | Medium | Companies: Amazon; Microsoft
• LC236 — Lowest Common Ancestor of a Binary Tree | Tree | Medium | Companies: Amazon; Facebook; Google; Microsoft
• LC98 — Validate Binary Search Tree | Tree | Medium | Companies: Amazon; Facebook; Google; Microsoft
• LC105 — Construct Binary Tree from Preorder and Inorder Traversal | Tree | Medium | Companies: Amazon; Microsoft
• LC124 — Binary Tree Maximum Path Sum | Tree | Hard | Companies: Amazon; Google; Meta

Day 12 (2026-01-10) — Trie

• LC208 — Implement Trie (Prefix Tree) | Trie | Medium | Companies: Amazon; Google; Microsoft
• LC211 — Design Add and Search Words Data Structure | Trie | Medium | Companies: Amazon; Facebook; Google
• LC212 — Word Search II | Trie | Hard | Companies: Amazon; Google; Microsoft
• LC1268 — Search Suggestions System | Trie | Medium | Companies: Amazon; Google
• LC648 — Replace Words | Trie | Medium | Companies: Amazon; Google
• LC720 — Longest Word in Dictionary | Trie | Medium | Companies: Amazon; Google

Day 13 (2026-01-11) — Graph BFS/DFS

• LC200 — Number of Islands | Graph | Medium | Companies: Amazon; Google; Microsoft
• LC133 — Clone Graph | Graph | Medium | Companies: Amazon; Google; Meta; Microsoft
• LC417 — Pacific Atlantic Water Flow | Graph | Medium | Companies: Amazon; Google; Microsoft
• LC994 — Rotting Oranges | Graph | Medium | Companies: Amazon; Microsoft
• LC127 — Word Ladder | Graph | Hard | Companies: Amazon; Facebook; Google; Microsoft
• LC542 — 01 Matrix | Graph | Medium | Companies: Amazon; Google; Microsoft

Day 14 (2026-01-12) — REVISION: 3 new (2H+1M)

• LC269 — Alien Dictionary | Graph | Hard | Companies: Amazon; Google; Meta
• LC968 — Binary Tree Cameras | Tree | Hard | Companies: Amazon; Google
• LC130 — Surrounded Regions | Graph | Medium | Companies: Amazon; Google; Microsoft

Day 15 (2026-01-13) — Graph topo/Union-Find

• LC207 — Course Schedule | Graph | Medium | Companies: Amazon; Google; Microsoft
• LC210 — Course Schedule II | Graph | Medium | Companies: Amazon; Google; Microsoft
• LC684 — Redundant Connection | Graph | Medium | Companies: Amazon; Google
• LC721 — Accounts Merge | Graph | Medium | Companies: Amazon; Google; Microsoft
• LC329 — Longest Increasing Path in a Matrix | DP | Hard | Companies: Amazon; Google; Microsoft
• LC332 — Reconstruct Itinerary | Graph | Hard | Companies: Amazon; Google; Meta; Microsoft

Day 16 (2026-01-14) — Graph shortest paths

• LC743 — Network Delay Time | Graph | Medium | Companies: Amazon; Google; Microsoft
• LC787 — Cheapest Flights Within K Stops | Graph | Medium | Companies: Amazon; Google; Microsoft
• LC1514 — Path with Maximum Probability | Graph | Medium | Companies: Amazon; Google
• LC1631 — Path With Minimum Effort | Graph | Medium | Companies: Amazon; Google
• LC778 — Swim in Rising Water | Graph | Hard | Companies: Amazon; Google
• LC847 — Shortest Path Visiting All Nodes | Graph | Hard | Companies: Amazon; Google; Meta

Day 17 (2026-01-15) — DP baseline

• LC70 — Climbing Stairs | DP | Easy | Companies: Amazon; Google
• LC198 — House Robber | DP | Medium | Companies: Amazon; Google; Microsoft
• LC322 — Coin Change | DP | Medium | Companies: Amazon; Google; Microsoft
• LC300 — Longest Increasing Subsequence | DP | Medium | Companies: Amazon; Google; Microsoft
• LC62 — Unique Paths | DP | Medium | Companies: Amazon; Google; Microsoft
• LC72 — Edit Distance | DP | Hard | Companies: Amazon; Google; Microsoft

Day 18 (2026-01-16) — DP knapsack/subset/coin

• LC416 — Partition Equal Subset Sum | DP | Medium | Companies: Amazon; Google; Microsoft
• LC494 — Target Sum | DP | Medium | Companies: Amazon; Google
• LC518 — Coin Change II | DP | Medium | Companies: Amazon; Google
• LC1049 — Last Stone Weight II | DP | Medium | Companies: Amazon; Google
• LC879 — Profitable Schemes | DP | Hard | Companies: Amazon; Google
• LC1155 — Number of Dice Rolls With Target Sum | DP | Medium | Companies: Amazon; Google

Day 19 (2026-01-17) — DP LCS/edit/palindrome

• LC1143 — Longest Common Subsequence | DP | Medium | Companies: Amazon; Google; Microsoft
• LC516 — Longest Palindromic Subsequence | DP | Medium | Companies: Amazon; Google
• LC5 — Longest Palindromic Substring | DP | Medium | Companies: Amazon; Google; Microsoft
• LC647 — Palindromic Substrings | DP | Medium | Companies: Amazon; Google
• LC44 — Wildcard Matching | DP | Hard | Companies: Amazon; Google; Microsoft
• LC97 — Interleaving String | DP | Medium | Companies: Amazon; Google

Day 20 (2026-01-18) — Backtracking baseline

• LC78 — Subsets | Backtracking | Medium | Companies: Amazon; Google; Microsoft
• LC46 — Permutations | Backtracking | Medium | Companies: Amazon; Google; Microsoft
• LC39 — Combination Sum | Backtracking | Medium | Companies: Amazon; Google; Microsoft
• LC40 — Combination Sum II | Backtracking | Medium | Companies: Amazon; Google
• LC131 — Palindrome Partitioning | Backtracking | Medium | Companies: Amazon; Google
• LC51 — N-Queens | Backtracking | Hard | Companies: Amazon; Google; Microsoft

Day 21 (2026-01-19) — REVISION: 3 new (2H+1M)

• LC312 — Burst Balloons | DP | Hard | Companies: Amazon; Google
• LC301 — Remove Invalid Parentheses | Backtracking | Hard | Companies: Amazon; Google; Meta
• LC139 — Word Break | DP | Medium | Companies: Amazon; Google; Microsoft

Day 22 (2026-01-20) — Stack advanced

• LC496 — Next Greater Element I | Stack | Easy | Companies: Amazon; Google
• LC901 — Online Stock Span | Stack | Medium | Companies: Amazon; Google; Microsoft
• LC394 — Decode String | Stack | Medium | Companies: Amazon; Google; Microsoft
• LC316 — Remove Duplicate Letters | Stack | Medium | Companies: Amazon; Google; Microsoft
• LC224 — Basic Calculator | Stack | Hard | Companies: Amazon; Google; Meta; Microsoft
• LC402 — Remove K Digits | Stack | Medium | Companies: Amazon; Google

Day 23 (2026-01-21) — Bit manipulation

• LC136 — Single Number | Bit Manipulation | Easy | Companies: Amazon; Google; Microsoft
• LC371 — Sum of Two Integers | Bit Manipulation | Medium | Companies: Amazon; Google; Microsoft
• LC260 — Single Number III | Bit Manipulation | Medium | Companies: Amazon; Google; Microsoft
• LC338 — Counting Bits | Bit Manipulation | Medium | Companies: Amazon; Google
• LC268 — Missing Number | Bit Manipulation | Easy | Companies: Amazon; Google; Microsoft
• LC318 — Maximum Product of Word Lengths | Bit Manipulation | Medium | Companies: Amazon; Google

Day 24 (2026-01-22) — Greedy

• LC455 — Assign Cookies | Greedy | Easy | Companies: Amazon; Google
• LC134 — Gas Station | Greedy | Medium | Companies: Amazon; Google
• LC763 — Partition Labels | Greedy | Medium | Companies: Amazon; Google
• LC55 — Jump Game | Greedy | Medium | Companies: Amazon; Google; Microsoft
• LC406 — Queue Reconstruction by Height | Greedy | Medium | Companies: Amazon; Google; Microsoft
• LC295 — Find Median from Data Stream | Heap | Hard | Companies: Amazon; Google; Microsoft

Day 25 (2026-01-23) — Design DS

• LC146 — LRU Cache | Design DS | Medium | Companies: Amazon; Google; Microsoft
• LC380 — Insert Delete GetRandom O(1) | Design DS | Medium | Companies: Amazon; Google; Microsoft
• LC981 — Time Based Key-Value Store | Design DS | Medium | Companies: Amazon; Google; Meta (Facebook)
• LC355 — Design Twitter | Design DS | Medium | Companies: Amazon; Google; Meta; Microsoft
• LC535 — Encode and Decode TinyURL | Design DS | Medium | Companies: Amazon; Google; Microsoft
• LC76 — Minimum Window Substring | Sliding Window | Hard | Companies: Amazon; Google; Meta (Facebook); Microsoft

Day 26 (2026-01-24) — Tree advanced

• LC297 — Serialize and Deserialize Binary Tree | Tree | Hard | Companies: Amazon; Google; Microsoft
• LC437 — Path Sum III | Tree | Medium | Companies: Amazon; Google
• LC543 — Diameter of Binary Tree | Tree | Easy | Companies: Amazon; Google; Microsoft
• LC124 — Binary Tree Maximum Path Sum | Tree | Hard | Companies: Amazon; Google; Meta
• LC337 — House Robber III | Tree | Medium | Companies: Amazon; Google
• LC450 — Delete Node in a BST | Tree | Medium | Companies: Amazon; Google; Microsoft

Day 27 (2026-01-25) — Graph hard mix

• LC399 — Evaluate Division | Graph | Medium | Companies: Amazon; Google; Meta; Microsoft
• LC310 — Minimum Height Trees | Graph | Medium | Companies: Amazon; Google; Microsoft
• LC785 — Is Graph Bipartite? | Graph | Medium | Companies: Amazon; Google; Microsoft
• LC269 — Alien Dictionary | Graph | Hard | Companies: Amazon; Google; Meta
• LC332 — Reconstruct Itinerary | Graph | Hard | Companies: Amazon; Google; Meta; Microsoft
• LC115 — Distinct Subsequences | DP | Hard | Companies: Amazon; Google; Microsoft

Day 28 (2026-01-26) — REVISION: 3 new (2H+1M)

• LC871 — Minimum Number of Refueling Stops | DP | Hard | Companies: Amazon; Google; Microsoft
• LC407 — Trapping Rain Water II | Graph | Hard | Companies: Amazon; Google; Microsoft
• LC528 — Random Pick with Weight | Binary Search | Medium | Companies: Amazon; Google

Day 29 (2026-01-27) — DP hard mix

• LC650 — 2 Keys Keyboard | DP | Medium | Companies: Amazon; Google
• LC198 — House Robber | DP | Medium | Companies: Amazon; Google; Microsoft
• LC312 — Burst Balloons | DP | Hard | Companies: Amazon; Google
• LC279 — Perfect Squares | DP | Medium | Companies: Amazon; Google; Microsoft
• LC403 — Frog Jump | DP | Hard | Companies: Amazon; Google
• LC871 — Minimum Number of Refueling Stops | DP | Hard | Companies: Amazon; Google; Microsoft

Day 30 (2026-01-28) — Heap/Intervals advanced

• LC703 — Kth Largest Element in a Stream | Heap | Easy | Companies: Amazon; Google
• LC767 — Reorganize String | Heap | Medium | Companies: Amazon; Google
• LC973 — K Closest Points to Origin | Heap | Medium | Companies: Amazon; Google
• LC253 — Meeting Rooms II | Intervals | Medium | Companies: Amazon; Facebook; Google; Microsoft
• LC480 — Sliding Window Median | Heap | Hard | Companies: Amazon; Google
• LC239 — Sliding Window Maximum | Stack | Hard | Companies: Amazon; Google; Microsoft

Day 31 (2026-01-29) — Binary Search advanced

• LC1011 — Capacity To Ship Packages Within D Days | Binary Search | Medium | Companies: Amazon; Google; Microsoft
• LC875 — Koko Eating Bananas | Binary Search | Medium | Companies: Amazon; Google
• LC410 — Split Array Largest Sum | Binary Search | Hard | Companies: Amazon; Google; Microsoft
• LC74 — Search a 2D Matrix | Binary Search | Medium | Companies: Amazon; Google; Microsoft
• LC981 — Time Based Key-Value Store | Design DS | Medium | Companies: Amazon; Google; Meta (Facebook)
• LC4 — Median of Two Sorted Arrays | Binary Search | Hard | Companies: Amazon; Google; Microsoft

Day 32 (2026-01-30) — Hashing/Prefix + Strings

• LC238 — Product of Array Except Self | Hashing/Prefix | Medium | Companies: Amazon; Google; Microsoft
• LC523 — Continuous Subarray Sum | Hashing/Prefix | Medium | Companies: Amazon; Google; Microsoft
• LC560 — Subarray Sum Equals K | Hashing/Prefix | Medium | Companies: Amazon; Google; Meta (Facebook)
• LC242 — Valid Anagram | Hashing/Prefix | Easy | Companies: Amazon; Google; Microsoft
• LC44 — Wildcard Matching | DP | Hard | Companies: Amazon; Google; Microsoft
• LC72 — Edit Distance | DP | Hard | Companies: Amazon; Google; Microsoft

Day 33 (2026-01-31) — Backtracking harder

• LC90 — Subsets II | Backtracking | Medium | Companies: Amazon; Google; Microsoft
• LC47 — Permutations II | Backtracking | Medium | Companies: Amazon; Google
• LC79 — Word Search | Backtracking | Medium | Companies: Amazon; Google; Microsoft
• LC17 — Letter Combinations of a Phone Number | Backtracking | Medium | Companies: Amazon; Google; Microsoft
• LC37 — Sudoku Solver | Backtracking | Hard | Companies: Amazon; Google; Microsoft
• LC52 — N-Queens II | Backtracking | Hard | Companies: Amazon; Google

Day 34 (2026-02-01) — Simulation/Math

• LC54 — Spiral Matrix | Simulation | Medium | Companies: Amazon; Google; Microsoft
• LC43 — Multiply Strings | Math | Medium | Companies: Amazon; Google; Microsoft
• LC48 — Rotate Image | Simulation | Medium | Companies: Amazon; Google; Microsoft
• LC227 — Basic Calculator II | Simulation | Medium | Companies: Amazon; Google; Microsoft
• LC10 — Regular Expression Matching | DP | Hard | Companies: Amazon; Google; Meta
• LC239 — Sliding Window Maximum | Stack | Hard | Companies: Amazon; Google; Microsoft

Day 35 (2026-02-02) — REVISION: 3 new (2H+1M)

• LC25 — Reverse Nodes in k-Group | Two Pointers | Hard | Companies: Amazon; Google; Microsoft
• LC309 — Best Time to Buy and Sell Stock with Cooldown | DP | Medium | Companies: Amazon; Google
• LC140 — Word Break II | DP | Hard | Companies: Amazon; Google

Day 36 (2026-02-03) — Company focus: Amazon

• LC200 — Number of Islands | Graph | Medium | Companies: Amazon; Google; Microsoft
• LC56 — Merge Intervals | Intervals | Medium | Companies: Amazon; Facebook; Google; Microsoft
• LC146 — LRU Cache | Design DS | Medium | Companies: Amazon; Google; Microsoft
• LC238 — Product of Array Except Self | Hashing/Prefix | Medium | Companies: Amazon; Google; Microsoft
• LC297 — Serialize and Deserialize Binary Tree | Tree | Hard | Companies: Amazon; Google; Microsoft
• LC410 — Split Array Largest Sum | Binary Search | Hard | Companies: Amazon; Google; Microsoft

Day 37 (2026-02-04) — Company focus: Google

• LC76 — Minimum Window Substring | Sliding Window | Hard | Companies: Amazon; Google; Meta (Facebook); Microsoft
• LC1248 — Count Number of Nice Subarrays | Sliding Window | Medium | Companies: Amazon; Google
• LC560 — Subarray Sum Equals K | Hashing/Prefix | Medium | Companies: Amazon; Google; Meta (Facebook)
• LC875 — Koko Eating Bananas | Binary Search | Medium | Companies: Amazon; Google
• LC127 — Word Ladder | Graph | Hard | Companies: Amazon; Facebook; Google; Microsoft
• LC212 — Word Search II | Trie | Hard | Companies: Amazon; Google; Microsoft

Day 38 (2026-02-05) — Company focus: Meta

• LC3 — Longest Substring Without Repeating Characters | Sliding Window | Medium | Companies: Adobe; Amazon; Bloomberg; Google; Microsoft
• LC49 — Group Anagrams | Hashing/Prefix | Medium | Companies: Amazon; Bloomberg; Google; Meta; Microsoft
• LC42 — Trapping Rain Water | Stack | Hard | Companies: Amazon; Google; Meta; Microsoft
• LC560 — Subarray Sum Equals K | Hashing/Prefix | Medium | Companies: Amazon; Google; Meta (Facebook)
• LC269 — Alien Dictionary | Graph | Hard | Companies: Amazon; Google; Meta
• LC133 — Clone Graph | Graph | Medium | Companies: Amazon; Google; Meta; Microsoft

Day 39 (2026-02-06) — Company focus: Microsoft

• LC102 — Binary Tree Level Order Traversal | Tree | Medium | Companies: Amazon; Microsoft
• LC1143 — Longest Common Subsequence | DP | Medium | Companies: Amazon; Google; Microsoft
• LC621 — Task Scheduler | Heap | Medium | Companies: Amazon; Google; Microsoft
• LC34 — Find First and Last Position of Element in Sorted Array | Binary Search | Medium | Companies: Amazon; LinkedIn; Microsoft
• LC4 — Median of Two Sorted Arrays | Binary Search | Hard | Companies: Amazon; Google; Microsoft
• LC84 — Largest Rectangle in Histogram | Stack | Hard | Companies: Amazon; Google; Microsoft

Day 40 (2026-02-07) — Mixed set #1

• LC139 — Word Break | DP | Medium | Companies: Amazon; Google; Microsoft
• LC310 — Minimum Height Trees | Graph | Medium | Companies: Amazon; Google; Microsoft
• LC236 — Lowest Common Ancestor of a Binary Tree | Tree | Medium | Companies: Amazon; Facebook; Google; Microsoft
• LC44 — Wildcard Matching | DP | Hard | Companies: Amazon; Google; Microsoft
• LC224 — Basic Calculator | Stack | Hard | Companies: Amazon; Google; Meta; Microsoft
• LC410 — Split Array Largest Sum | Binary Search | Hard | Companies: Amazon; Google; Microsoft

Day 41 (2026-02-08) — Mixed set #2 — 7 problems

• LC300 — Longest Increasing Subsequence | DP | Medium | Companies: Amazon; Google; Microsoft
• LC785 — Is Graph Bipartite? | Graph | Medium | Companies: Amazon; Google; Microsoft
• LC98 — Validate Binary Search Tree | Tree | Medium | Companies: Amazon; Facebook; Google; Microsoft
• LC739 — Daily Temperatures | Stack | Medium | Companies: Amazon; Google
• LC115 — Distinct Subsequences | DP | Hard | Companies: Amazon; Google; Microsoft
• LC312 — Burst Balloons | DP | Hard | Companies: Amazon; Google
• LC847 — Shortest Path Visiting All Nodes | Graph | Hard | Companies: Amazon; Google; Meta

Day 42 (2026-02-09) — REVISION: 3 new (2H+1M)

• LC301 — Remove Invalid Parentheses | Backtracking | Hard | Companies: Amazon; Google; Meta
• LC871 — Minimum Number of Refueling Stops | DP | Hard | Companies: Amazon; Google; Microsoft
• LC162 — Find Peak Element | Binary Search | Medium | Companies: Amazon; Google; Microsoft

Day 43 (2026-02-10) — Weakness fill

• LC322 — Coin Change | DP | Medium | Companies: Amazon; Google; Microsoft
• LC399 — Evaluate Division | Graph | Medium | Companies: Amazon; Google; Meta; Microsoft
• LC71 — Simplify Path | Stack | Medium | Companies: Amazon; Google; Microsoft
• LC560 — Subarray Sum Equals K | Hashing/Prefix | Medium | Companies: Amazon; Google; Meta (Facebook)
• LC778 — Swim in Rising Water | Graph | Hard | Companies: Amazon; Google
• LC297 — Serialize and Deserialize Binary Tree | Tree | Hard | Companies: Amazon; Google; Microsoft

Day 44 (2026-02-11) — Strings + Stack

• LC8 — String to Integer (atoi) | Strings | Medium | Companies: Amazon; Google; Microsoft
• LC49 — Group Anagrams | Hashing/Prefix | Medium | Companies: Amazon; Bloomberg; Google; Meta; Microsoft
• LC394 — Decode String | Stack | Medium | Companies: Amazon; Google; Microsoft
• LC316 — Remove Duplicate Letters | Stack | Medium | Companies: Amazon; Google; Microsoft
• LC10 — Regular Expression Matching | DP | Hard | Companies: Amazon; Google; Meta
• LC32 — Longest Valid Parentheses | Stack | Hard | Companies: Amazon; Google; Meta; Microsoft

Day 45 (2026-02-12) — DP + Binary Search + Greedy

• LC875 — Koko Eating Bananas | Binary Search | Medium | Companies: Amazon; Google
• LC1011 — Capacity To Ship Packages Within D Days | Binary Search | Medium | Companies: Amazon; Google; Microsoft
• LC198 — House Robber | DP | Medium | Companies: Amazon; Google; Microsoft
• LC309 — Best Time to Buy and Sell Stock with Cooldown | DP | Medium | Companies: Amazon; Google
• LC410 — Split Array Largest Sum | Binary Search | Hard | Companies: Amazon; Google; Microsoft
• LC72 — Edit Distance | DP | Hard | Companies: Amazon; Google; Microsoft

Day 46 (2026-02-13) — Graph + Tree combo

• LC200 — Number of Islands | Graph | Medium | Companies: Amazon; Google; Microsoft
• LC310 — Minimum Height Trees | Graph | Medium | Companies: Amazon; Google; Microsoft
• LC743 — Network Delay Time | Graph | Medium | Companies: Amazon; Google; Microsoft
• LC269 — Alien Dictionary | Graph | Hard | Companies: Amazon; Google; Meta
• LC297 — Serialize and Deserialize Binary Tree | Tree | Hard | Companies: Amazon; Google; Microsoft
• LC124 — Binary Tree Maximum Path Sum | Tree | Hard | Companies: Amazon; Google; Meta

Day 47 (2026-02-14) — Stack/Heap/Design hard mix

• LC621 — Task Scheduler | Heap | Medium | Companies: Amazon; Google; Microsoft
• LC981 — Time Based Key-Value Store | Design DS | Medium | Companies: Amazon; Google; Meta (Facebook)
• LC739 — Daily Temperatures | Stack | Medium | Companies: Amazon; Google
• LC44 — Wildcard Matching | DP | Hard | Companies: Amazon; Google; Microsoft
• LC115 — Distinct Subsequences | DP | Hard | Companies: Amazon; Google; Microsoft
• LC127 — Word Ladder | Graph | Hard | Companies: Amazon; Facebook; Google; Microsoft

Day 48 (2026-02-15) — Final hard mix — 8 problems

• LC1143 — Longest Common Subsequence | DP | Medium | Companies: Amazon; Google; Microsoft
• LC236 — Lowest Common Ancestor of a Binary Tree | Tree | Medium | Companies: Amazon; Facebook; Google; Microsoft
• LC399 — Evaluate Division | Graph | Medium | Companies: Amazon; Google; Meta; Microsoft
• LC312 — Burst Balloons | DP | Hard | Companies: Amazon; Google
• LC410 — Split Array Largest Sum | Binary Search | Hard | Companies: Amazon; Google; Microsoft
• LC224 — Basic Calculator | Stack | Hard | Companies: Amazon; Google; Meta; Microsoft
• LC847 — Shortest Path Visiting All Nodes | Graph | Hard | Companies: Amazon; Google; Meta
• LC212 — Word Search II | Trie | Hard | Companies: Amazon; Google; Microsoft

Day 49 (2026-02-16) — REVISION: 3 new (2H+1M)

• LC37 — Sudoku Solver | Backtracking | Hard | Companies: Amazon; Google; Microsoft
• LC407 — Trapping Rain Water II | Graph | Hard | Companies: Amazon; Google; Microsoft
• LC560 — Subarray Sum Equals K | Hashing/Prefix | Medium | Companies: Amazon; Google; Meta (Facebook)

Day 50 (2026-02-17) — FINAL BOSS: 30 new (20M+10H)

• LC581 — Shortest Unsorted Continuous Subarray | Two Pointers | Medium | Companies: Adobe; Amazon; Microsoft
• LC1493 — Longest Subarray of 1’s After Deleting One Element | Sliding Window | Medium | Companies: Amazon; Google
• LC808 — Soup Servings | DP | Medium | Companies: Amazon; Google
• LC918 — Maximum Sum Circular Subarray | Stack | Medium | Companies: Amazon; Google
• LC221 — Maximal Square | DP | Medium | Companies: Amazon; Google; Microsoft
• LC229 — Majority Element II | Hashing/Prefix | Medium | Companies: Amazon; Google; Microsoft
• LC767 — Reorganize String | Heap | Medium | Companies: Amazon; Google
• LC417 — Pacific Atlantic Water Flow | Graph | Medium | Companies: Amazon; Google; Microsoft
• LC452 — Minimum Number of Arrows to Burst Balloons | Intervals | Medium | Companies: Amazon; Google
• LC17 — Letter Combinations of a Phone Number | Backtracking | Medium | Companies: Amazon; Google; Microsoft
• LC394 — Decode String | Stack | Medium | Companies: Amazon; Google; Microsoft
• LC567 — Permutation in String | Sliding Window | Medium | Companies: Amazon; Google
• LC494 — Target Sum | DP | Medium | Companies: Amazon; Google
• LC684 — Redundant Connection | Graph | Medium | Companies: Amazon; Google
• LC49 — Group Anagrams | Hashing/Prefix | Medium | Companies: Amazon; Bloomberg; Google; Meta; Microsoft
• LC300 — Longest Increasing Subsequence | DP | Medium | Companies: Amazon; Google; Microsoft
• LC646 — Maximum Length of Pair Chain | Greedy | Medium | Companies: Amazon; Google
• LC994 — Rotting Oranges | Graph | Medium | Companies: Amazon; Microsoft
• LC981 — Time Based Key-Value Store | Design DS | Medium | Companies: Amazon; Google; Meta (Facebook)
• LC875 — Koko Eating Bananas | Binary Search | Medium | Companies: Amazon; Google
• LC124 — Binary Tree Maximum Path Sum | Tree | Hard | Companies: Amazon; Google; Meta
• LC10 — Regular Expression Matching | DP | Hard | Companies: Amazon; Google; Meta
• LC76 — Minimum Window Substring | Sliding Window | Hard | Companies: Amazon; Google; Meta (Facebook); Microsoft
• LC239 — Sliding Window Maximum | Stack | Hard | Companies: Amazon; Google; Microsoft
• LC4 — Median of Two Sorted Arrays | Binary Search | Hard | Companies: Amazon; Google; Microsoft
• LC312 — Burst Balloons | DP | Hard | Companies: Amazon; Google
• LC37 — Sudoku Solver | Backtracking | Hard | Companies: Amazon; Google; Microsoft
• LC127 — Word Ladder | Graph | Hard | Companies: Amazon; Facebook; Google; Microsoft
• LC295 — Find Median from Data Stream | Heap | Hard | Companies: Amazon; Google; Microsoft
• LC212 — Word Search II | Trie | Hard | Companies: Amazon; Google; Microsoft

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