Hard LeetCode-Java-Solutions S.no Coding Problem 1 Concatenated Words 2 Remove Invalid Parentheses 3 First Missing Positive 4 Frog Jump 5 Sliding Window Median 6 Edit Distance 7 Merge K Sorted Lists 8 Sliding Window Maximum 9 Text Justification 10 Basic Calculator III 11 Insert Interval 12 Integer to English Words 13 Median of Two Sorted Arrays 14 Divide Array Into Increasing Sequences 15 Word Break II 16 Maximum Number of Non-Overlapping Substrings 17 Subarrays with K Different Integers 18 Parallel Courses 19 LFU Cache 20 Word Search II 21 K Empty Slots 22 Employee Free Time 23 N-Queens 24 Longest Palindrome Product 25 Odd Even Jump 26 Palindrome Pairs 27 Stream of Characters 28 Cut Off Trees for Golf Event 29 Minimize Deviation in Array 30 Minimum Cost to Hire K Workers 31 Number of Valid Subarrays 32 Substring with Concatenation of All Words 33 Number of Paths with Max Score 34 Design Search Autocomplete System 35 LRU Cache 36 Number of Squareful Arrays 37 Robot Room Cleaner 38 Minimum Window Substring 39 Hard 40 Parsing A Boolean Expression 41 Trapping Rain Water 42 Optimal Account Balancing 43 Find Median From Data Stream 44 Find Minimum in Rotated Sorted Array II 45 Longest Substring with At Most Two Distinct Characters 46 Number of Submatrices That Sum to Target 47 Candy 48 Shortest Distance from All Buildings 49 Recover a Tree From Preorder Traversal 50 Longest Increasing Path in a Matrix 51 Interleaving String 52 Closest Binary Search Tree Values II 53 Basic Calculator 54 Prefix and Suffix Search 55 Valid Number 56 Maximum Frequency Stack 57 Reverse Nodes in k-Group 58 Longest Substring with At Most K Distinct Characters 59 Serialize and Deserialize N-ary Tree 60 Serialize and Deserialize a Binary Tree 61 Binary Tree PostOrder Traversal 62 Unique Paths III 63 Insert Delete GetRandom O(1) - Duplicates Allowed 64 Maximum Sum BST in Binary Tree 65 Binary Tree Maximum Path Sum 66 Largest Rectangle in Histogram