Hard LeetCode-Java-Solutions S.no Coding Problem 1 Concatenated Words 2 Minimum Cost to Make Array Equal 3 Max Stack 4 Course Schedule III 5 Binary Tree Cameras 6 Remove Invalid Parentheses 7 First Missing Positive 8 Reconstruct Itinerary 9 Frog Jump 10 Sort Items by Groups Respecting Dependencies 11 Shortest Path Visiting All Nodes 12 Critical Connections in a Network 13 Sliding Window Median 14 Edit Distance 15 Checking Existence of Edge Length Limited Paths 16 Perfect Rectangle 17 Minimum Window Subsequence 18 Remove Max Number of Edges to Keep Graph Fully Traversable 19 K Inverse Pairs Array 20 Merge K Sorted Lists 21 Minimum Replacements to Sort the Array 22 Design Movie Rental System 23 Sliding Window Maximum 24 My Calendar III 25 Longest Cycle in a Graph 26 Text Justification 27 Design In-Memory File System 28 Basic Calculator III 29 Integer to English Words 30 Naming a Company 31 Minimum Number of Refueling Stops 32 Rearrange String k Distance Apart 33 Make Array Strictly Increasing 34 Median of Two Sorted Arrays 35 Vertical Order Traversal Of a Binary Tree 36 Divide Array Into Increasing Sequences 37 Word Break II 38 Maximum Number of Non-Overlapping Substrings 39 Paint House II 40 Subarrays with K Different Integers 41 Maximum Performance of a Team 42 Jump Game IV 43 Paint House III 44 LFU Cache 45 Scramble String 46 Word Search II 47 K Empty Slots 48 Employee Free Time 49 Maximize Score After N Operations 50 Max Points on a Line 51 The Skyline Problem 52 N-Queens 53 Longest Palindrome Product 54 Odd Even Jump 55 Palindrome Pairs 56 Stream of Characters 57 Cut Off Trees for Golf Event 58 Kth Smallest Number in Multiplication Table 59 String Compression II 60 Minimize Deviation in Array 61 Minimum Cost to Hire K Workers 62 Find the Longest Valid Obstacle Course at Each Position 63 Number of Valid Subarrays 64 Maximum Value of K Coins From Piles 65 Substring with Concatenation of All Words 66 Number of Paths with Max Score 67 Profitable Schemes 68 Design Search Autocomplete System 69 Number of Squareful Arrays 70 N-Queens II 71 Robot Room Cleaner 72 Poor Pigs 73 Minimum Window Substring 74 Number of Ways of Cutting a Pizza 75 Hard 76 Parsing A Boolean Expression 77 Trapping Rain Water 78 Similar String Groups 79 Number of Ways to Form a Target String Given a Dictionary 80 Find the Kth Smallest Sum of a Matrix With Sorted Rows 81 Optimal Account Balancing 82 Design Skiplist 83 Wildcard Matching 84 Expression Add Operators 85 Count of Smaller Numbers After Self 86 Number of Ways to Reorder Array to Get Same BST 87 Find Median from Data Stream 88 Best Time to Buy and Sell Stock IV 89 Find Minimum in Rotated Sorted Array II 90 Longest Valid Parentheses 91 Stone Game III 92 Reducing Dishes 93 Count Subarrays With Fixed Bounds 94 Stamping The Sequence 95 Number of Submatrices That Sum to Target 96 Candy 97 Minimum Insertion Steps to Make a String Palindrome 98 Shortest Distance from All Buildings 99 Recover a Tree From Preorder Traversal 100 Count Vowels Permutation 101 Longest Increasing Path in a Matrix 102 Maximum Profit in Job Scheduling 103 Closest Binary Search Tree Values II 104 Basic Calculator 105 Alien Dictionary 106 Prefix and Suffix Search 107 Construct Target Array With Multiple Sums 108 Tallest Billboard 109 Largest Color Value in a Directed Graph 110 Valid Number 111 Dice Roll Simulation 112 Maximum Frequency Stack 113 Reverse Nodes in k-Group 114 Serialize and Deserialize N-ary Tree 115 Serialize and Deserialize a Binary Tree 116 Minimum Difficulty of a Job Schedule 117 Unique Paths III 118 Restore The Array 119 IPO 120 Insert Delete GetRandom O(1) - Duplicates Allowed 121 Add Edges to Make Degrees of All Nodes Even 122 Maximum Sum BST in Binary Tree 123 Binary Tree Maximum Path Sum 124 Largest Rectangle in Histogram