LeetCode => JAVA + DSA SOLUTION By [SANJANA SINGH] Difficulty Challenge Solution Easy 1. Two Sum Solution Easy 26. Remove Duplicates from Sorted Array Solution Easy 1854. Maximum Population Year[Important] Solution Easy 1886. Determine Whether Matrix Can Be Obtained By Rotation [Important] Solution Easy 1304. Find N Unique Integers Sum up to Zero Solution Easy 566. Reshape the Matrix Solution Easy 66. Plus One Solution Easy 414. Third Maximum Number Solution Easy 1122. Relative Sort Array Solution Easy 1464. Maximum Product of Two Elements in an Array Solution Easy 1991. Find the Middle Index in Array Solution Easy 268. Missing Number Solution Easy 283. Move Zeroes Solution Easy 744. Find Smallest Letter Greater Than Target Solution Easy 14. Longest Common Prefix Solution Easy 35. Search Insert Position Solution Easy 69. Sqrt(x) Solution Easy 231. Power of Two Solution Easy 1480. Running Sum of 1d Array Solution Easy 1832. Check if the Sentence Is Pangram Solution Easy 1732. Find the Highest Altitude Solution Easy 1572. Matrix Diagonal Sum Solution Easy 1295. Find Numbers with Even Number of Digits Solution Easy 1470. Shuffle the Array Solution Easy 1920. Build Array from Permutation Solution Easy 1929. Concatenation of Array Solution Easy 1920. Build Array from Permutation Solution Easy 1672. Richest Customer Wealth Solution Easy 832. Flipping an Image Solution Easy 1295. Find Numbers with Even Number of Digits Solution Easy 867. Transpose Matrix Solution Easy 1108. Defanging an IP Address Solution Easy 1528. Shuffle String Solution Easy 1773. Count Items Matching a Rule Solution Easy 1678. Goal Parser Interpretation Solution Easy 1859. Sorting the Sentence Solution Easy 1662. Check If Two String Arrays are Equivalent Solution Easy 709. To Lower Case Solution Easy 1704. Determine if String Halves Are Alike Solution Easy 557. Reverse Words in a String III Solution Easy 1967. Number of Strings That Appear as Substrings in Word Solution Easy 657. Robot Return to Origin Solution Easy 168. Excel Sheet Column Title Solution Easy 28. Implement strStr() Solution Easy 125. Valid Palindrome Solution Easy 680. Valid Palindrome II Solution Easy 14. Longest Common Prefix Solution Easy 1668. Maximum Repeating Substring Solution Easy 58. Length of Last Word Solution Easy 1768. Merge Strings Alternately Solution Easy 2000. Reverse Prefix of Word Solution Easy 13. Roman to Integer Solution Easy 20. Valid Parentheses Solution Easy 278. First Bad Version Solution Easy 367. Valid Perfect Square Solution Easy 374. Guess Number Higher or Lower Solution Easy 441. Arranging Coins Solution Easy 744. Find Smallest Letter Greater Than Target Solution Easy 1539. Kth Missing Positive Number Solution Easy 349. Intersection of Two Arrays Solution Easy 1351. Count Negative Numbers in a Sorted Matrix Solution Easy 704. Binary Search Solution Easy 1608. Special Array With X Elements Greater Than or Equal X Solution Easy 1346. Check If N and Its Double Exist Solution Easy 888. Fair Candy Swap Solution Easy 350. Intersection of Two Arrays II Solution Easy 88. Merge Sorted Array Solution Easy 169. Majority Element Solution Easy 217. Contains Duplicate Solution Easy 268. Missing Number Solution Easy 2114. Maximum Number of Words Found in Sentences Solution Easy 771. Jewels and Stones Solution Easy 2011. Final Value of Variable After Performing Operations Solution Easy 628. Maximum Product of Three Numbers Solution Easy 905. Sort Array By Parity Solution Easy 922. Sort Array By Parity II Solution Easy 561. Array Partition I Solution Easy 455. Assign Cookies Solution Easy 1051. Height Checker Solution Easy 976. Largest Perimeter Triangle Solution Easy 977. Squares of a Sorted Array Solution Easy 1342. Number of Steps to Reduce a Number to Zero (#Recursion) Solution Easy 344. Reverse String (#Recursion) Solution Easy 509. Fibonacci Number (#DP) Solution Easy 326. Power of Three (#Recursion) Solution Easy 342. Power of Four (#Recursion) Solution Easy 21. Merge Two Sorted Lists (#Recursion) Solution Easy 203. Remove Linked List Elements (#Recursion) Solution Easy 206. Reverse Linked List (#Recursion) Solution Easy 234. Palindrome Linked List (#Recursion) Solution Easy 1137. N-th Tribonacci Number (#DP) Solution Easy 70. Climbing Stairs (#DP) Solution Easy 746. Min Cost Climbing Stairs (#DP) Solution Easy 796. Rotate String Solution Easy 94. Binary Tree Inorder Traversal(#TREE) Solution Easy 783. Minimum Distance Between BST Nodes(#TREE) Solution Easy 671. Second Minimum Node In a Binary Tree(#TREE) Solution Easy 112. Path Sum(#TREE) Solution Easy 144. Binary Tree Preorder Traversal(#TREE) Solution Easy 226. Invert Binary Tree(#TREE) Solution Easy 572. Subtree of Another Tree(#TREE) Solution Easy 938. Range Sum of BST (#TREE) Solution Easy 101. Symmetric Tree(#TREE) Solution Easy 108. Convert Sorted Array to Binary Search Tree(#TREE) Solution Easy 617. Merge Two Binary Trees(#TREE) Solution Easy 104. Maximum Depth of Binary Tree(#TREE) Solution Easy 100. Same Tree(#TREE) Solution Easy 530. Minimum Absolute Difference in BST (#TREE) Solution Easy 404. Sum of Left Leaves (#TREE) Solution Easy 110. Balanced Binary Tree (#TREE) Solution Easy 257. Binary Tree Paths(#Tree) Solution Easy 1025. Divisor Game (#DP) Solution Easy 121. Best Time to Buy and Sell Stock Solution Easy 724. Find Pivot Index Solution Easy 118. Pascal's Triangle (#Important) Solution Easy 415. Add Strings Solution Easy 242. Valid Anagram Solution Easy 409. Longest Palindrome Solution Easy 67. Add Binary Solution Easy 202. Happy Number Solution Easy 844. Backspace String Compare (#Stack) Solution Easy 496. Next Greater Element I (#Stack) Solution Easy 387. First Unique Character in a String Solution Easy 485. Max Consecutive Ones Solution Easy 383. Ransom Note Solution Easy 941. Valid Mountain Array Solution Easy 27. Remove Element Solution Easy 136. Single Number Solution Easy 645. Set Mismatch Solution Easy 1252. Cells with Odd Values in a Matrix Solution Easy 1389. Create Target Array in the Given Order Solution Easy 1512. Number of Good Pairs Solution Easy 145. Binary Tree Postorder Traversal Solution Easy 448. Find All Numbers Disappeared in an Array Solution Easy 637. Average of Levels in Binary Tree(#Tree) Solution Easy 925. Long Pressed Name Solution Easy 1002. Find Common Characters Solution Easy 1200. Minimum Absolute Difference Solution Easy 653. Two Sum IV - Input is a BST Solution Easy 190. Reverse Bits Solution Easy 191. Number of 1 Bits Solution Easy 1523. Count Odd Numbers in an Interval Range Solution Easy 1491. Average Salary Excluding the Minimum and Maximum Salary Solution Easy 1281. Subtract the Product and Sum of Digits of an Integer Solution Easy 219. Contains Duplicate II Solution Easy 2068. Check Whether Two Strings are Almost Equivalent Solution Easy 766. Toeplitz Matrix Solution Easy 1380. Lucky Numbers in a Matrix Solution Easy 1323. Maximum 69 Number Solution Easy 1544. Make The String Great Solution Easy 1047. Remove All Adjacent Duplicates In String Solution Easy 2465. Number of Distinct Averages Solution Easy 263. Ugly Number Solution Easy 1207. Unique Number of Occurrences Solution Easy 872. Leaf-Similar Trees Solution Easy 1971. Find if Path Exists in Graph Solution Easy 2389. Longest Subsequence With Limited Sum Solution Easy 290. Word Pattern Solution Easy 520. Detect Capital Solution Easy 944. Delete Columns to Make Sorted Solution Easy 232. Implement Queue using Stacks Solution Easy 605. Can Place Flowers Solution Easy 189. Rotate Array Solution Easy 2605. Form Smallest Number From Two Digit Arrays Solution Easy 1046. Last Stone Weight Solution Easy 258. Add Digits Solution Easy 1822. Sign of the Product of an Array Solution Easy 2215. Find the Difference of Two Arrays Solution Easy 392. Is Subsequence Solution Easy 205. Isomorphic Strings(HashMap) Solution Easy 228. Summary Ranges Solution Easy 705. Design HashSet Solution Easy 1232. Check If It Is a Straight Line Solution Easy 1502. Can Make Arithmetic Progression From Sequence Solution Easy 1351. Count Negative Numbers in a Sorted Matrix Solution Easy 859. Buddy Strings Solution Easy 111. Minimum Depth of Binary Tree Solution Easy 459. Repeated Substring Pattern Solution Easy 225. Implement Stack using Queues Solution Easy 1337. The K Weakest Rows in a Matrix Solution Easy 389. Find the Difference Solution Easy 706. Design HashMap Solution Easy Solution Easy Solution Medium 80. Remove Duplicates from Sorted Array II Solution Medium 34. Find First and Last Position of Element in Sorted Array Solution Medium 162. Find Peak Element Solution Medium 167. Two Sum II - Input Array Is Sorted Solution Medium 78. Subsets (#Backtraking) Solution Medium 90. Subsets II (#Backtraking) Solution Medium 46. Permutations(#Backtraking) Solution Medium 47. Permutations II (#Backtraking) Solution Medium 131. Palindrome Partitioning (#Backtraking) Solution Medium 39. Combination Sum (#Backtraking) Solution Medium 40. Combination Sum II(#Backtraking) Solution Medium 494. Target Sum (#Recursion) Solution Medium 1922. Count Good Numbers (#Recursion) Solution Medium 62. Unique Paths (#DP) Solution Medium 63. Unique Paths II (#DP) Solution Medium 64. Minimum Path Sum (#DP) Solution Medium 139. Word Break (#DP) Solution Medium 151. Reverse Words in a String Solution Medium 543. Diameter of Binary Tree(#Tree) Solution Medium 98. Validate Binary Search Tree(#Tree) Solution Medium 113. Path Sum II(#Tree) Solution Medium 2. Add Two Numbers(#LL) Solution Medium 77. Combinations (#Backtraking) Solution Medium 526. Beautiful Arrangement (#DP) Solution Medium 338. Counting Bits (#DP) Solution Medium 53. Maximum Subarray Solution Medium 852. Peak Index in a Mountain Array Solution Medium 7. Reverse Integer Solution Medium 453. Minimum Moves to Equal Array Elements(#MATH) Solution Medium 89. Gray Code Solution Medium 3. Longest Substring Without Repeating Characters(#String) Solution Medium 122. Best Time to Buy and Sell Stock II Solution Medium 15. 3Sum Solution Medium 238. Product of Array Except Self Solution Medium 56. Merge Intervals(#Array) Solution Medium 54. Spiral Matrix(#Array) Solution Medium 560. Subarray Sum Equals K (#Array) Solution Medium 31. Next Permutation(#Array) Solution Medium 11. Container With Most Water(#Array) Solution Medium 48. Rotate Image(#Array) Solution Medium 79. Word Search (#Array) Solution Medium 16. 3Sum Closest (#Array) Solution Medium 287. Find the Duplicate Number (#Array) Solution Medium 289. Game of Life(#Array) Solution Medium 18. 4Sum (#Array) Solution Medium 1010. Pairs of Songs With Total Durations Divisible by 60 (#Array) Solution Medium 1423. Maximum Points You Can Obtain from Cards (#Array) Solution Medium 1465. Maximum Area of a Piece of Cake After Horizontal and Vertical Cuts (#Array) Solution Medium 695. Max Area of Island (#Array) Solution Medium 532. K-diff Pairs in an Array (#Array) Solution Medium 1169. Invalid Transactions (#Array) Solution Medium 55. Jump Game (#Array) Solution Medium 200. Number of Islands Solution Medium 73. Set Matrix Zeroes Solution Medium 33. Search in Rotated Sorted Array Solution Medium 36. Valid Sudoku Solution Medium 417. Pacific Atlantic Water Flow Solution Medium 1249. Minimum Remove to Make Valid Parentheses (#String) Solution Medium 5. Longest Palindromic Substring (#String) Solution Medium 49. Group Anagrams (#String) Solution Medium 227. Basic Calculator II (#String) Solution Medium 12. Integer to Roman (#String) Solution Medium 71. Simplify Path (#String) Solution Medium 28. Find the Index of the First Occurrence in a String (#String) Solution Medium 429. N-ary Tree Level Order Traversal (#Tree) Solution Medium 814. Binary Tree Pruning (#Tree) Solution Medium 1996. The Number of Weak Characters in the Game Solution Medium 179. Largest Number Solution Medium 948. Bag of Tokens Solution Medium 1383. Maximum Performance of a Team Solution Medium 985. Sum of Even Numbers After Queries Solution Medium 718. Maximum Length of Repeated Subarray Solution Medium 1680. Concatenation of Consecutive Binary Numbers Solution Medium 763. Partition Labels Solution Medium 19. Remove Nth Node From End of List Solution Medium 838. Push Dominoes Solution Medium 1155. Number of Dice Rolls With Target Sum Solution Medium 623. Add One Row to Tree Solution Medium 981. Time Based Key-Value Store Solution Medium 729. My Calendar I Solution Medium 334. Increasing Triplet Subsequence Solution Medium 2095. Delete the Middle Node of a Linked List Solution Medium 1531. String Compression II Solution Medium 443. String Compression Solution Medium 692. Top K Frequent Words (#Comparator) Solution Medium 1239. Maximum Length of a Concatenated String with Unique Characters Solution Medium 523. Continuous Subarray Sum Solution Medium 2300. Successful Pairs of Spells and Potions Solution Medium 1706. Where Will the Ball Fall Solution Medium 433. Minimum Genetic Mutation Solution Medium 2131. Longest Palindrome by Concatenating Two Letter Words Solution Medium 2461. Maximum Sum of Distinct Subarrays With Length K Solution Medium 137. Single Number II Solution Medium 260. Single Number III Solution Medium 901. Online Stock Span Solution Medium 947. Most Stones Removed with Same Row or Column Solution Medium 222. Count Complete Tree Nodes Solution Medium 223. Rectangle Area Solution Medium 1926. Nearest Exit from Entrance in Maze Solution Medium 279. Perfect Squares Solution Medium 907. Sum of Subarray Minimums Solution Medium 2225. Find Players With Zero or One Losses Solution Medium 380. Insert Delete GetRandom O(1) Solution Medium 1657. Determine if Two Strings Are Close Solution Medium 451. Sort Characters By Frequency Solution Medium 2256. Minimum Average Difference Solution Medium 328. Odd Even Linked List Solution Medium 1026. Maximum Difference Between Node and Ancestor Solution Medium 1339. Maximum Product of Splitted Binary Tree Solution Medium 1143. Longest Common Subsequence Solution Medium 150. Evaluate Reverse Polish Notation Solution Medium 739. Daily Temperatures Solution Medium 841. Keys and Rooms Solution Medium 886. Possible Bipartition Solution Medium 2279. Maximum Bags With Full Capacity of Rocks Solution Medium 1962. Remove Stones to Minimize the Total Solution Medium 1877. Minimize Maximum Pair Sum in Array Solution Medium 2244. Minimum Rounds to Complete All Tasks Solution Medium 452. Minimum Number of Arrows to Burst Balloons Solution Medium 1833. Maximum Ice Cream Bars Solution Medium 134. Gas Station Solution Medium 1443. Minimum Time to Collect All Apples in a Tree Solution Medium 926. Flip String to Monotone Increasing Solution Medium 974. Subarray Sums Divisible by K Solution Medium 93. Restore IP Addresses Solution Medium 904. Fruit Into Baskets Solution Medium 442. Find All Duplicates in an Array Solution Medium 1162. As Far from Land as Possible Solution Medium 382. Linked List Random Node Solution Medium 109. Convert Sorted List to Binary Search Tree Solution Medium 129. Sum Root to Leaf Numbers Solution Medium 958. Check Completeness of a Binary Tree Solution Medium 106. Construct Binary Tree from Inorder and Postorder Traversal Solution Medium 208. Implement Trie (Prefix Tree) Solution Medium 1472. Design Browser History Solution Medium 216. Combination Sum III Solution Medium 2348. Number of Zero-Filled Subarrays Solution Medium 1466. Reorder Routes to Make All Paths Lead to the City Zero Solution Medium 2606. Find the Substring With Maximum Cost Solution Medium 2405. Optimal Partition of String Solution Medium 2439. Minimize Maximum of Array Solution Medium 1254. Number of Closed Islands Solution Medium 1020. Number of Enclaves Solution Medium 2390. Removing Stars From a String Solution Medium 516. Longest Palindromic Subsequence Solution Medium 662. Maximum Width of Binary Tree Solution Medium 2336. Smallest Number in Infinite Set Solution Medium 319. Bulb Switcher Solution Medium 649. Dota2 Senate Solution Medium 1456. Maximum Number of Vowels in a Substring of Given Length Solution Medium 1498. Number of Subsequences That Satisfy the Given Sum Condition Solution Medium 59. Spiral Matrix II Solution Medium 1035. Uncrossed Lines (DP) Solution Medium 128. Longest Consecutive Sequence Solution Medium 2140. Solving Questions With Brainpower Solution Medium 2466. Count Ways To Build Good Strings Solution Medium 155. Min Stack Solution Medium 24. Swap Nodes in Pairs(LL) Solution Medium 2130. Maximum Twin Sum of a Linked List Solution Medium 1557. Minimum Number of Vertices to Reach All Nodes Solution Medium 785. Is Graph Bipartite? Solution Medium 837. New 21 Game Solution Medium 1140. Stone Game II Solution Medium 1396. Design Underground System Solution Medium 1091. Shortest Path in Binary Matrix Solution Medium 2101. Detonate the Maximum Bombs Solution Medium 1376. Time Needed to Inform All Employees Solution Medium 547. Number of Provinces Solution Medium 1318. Minimum Flips to Make a OR b Equal to c Solution Medium 1802. Maximum Value at a Given Index in a Bounded Array Solution Medium 1146. Snapshot Array Solution Medium 2352. Equal Row and Column Pairs Solution Medium 1161. Maximum Level Sum of a Binary Tree Solution Medium 2090. K Radius Subarray Averages Solution Medium 714. Best Time to Buy and Sell Stock with Transaction Fee Solution Medium 1027. Longest Arithmetic Subsequence Solution Medium 2462. Total Cost to Hire K Workers Solution Medium 373. Find K Pairs with Smallest Sums Solution Medium 1514. Path with Maximum Probability Solution Medium 2305. Fair Distribution of Cookies Solution Medium 1493. Longest Subarray of 1's After Deleting One Element Solution Medium 2024. Maximize the Confusion of an Exam Solution Medium 802. Find Eventual Safe States Solution Medium 1218. Longest Arithmetic Subsequence of Given Difference Solution Medium 445. Add Two Numbers II Solution Medium 146. LRU Cache Solution Medium 435. Non-overlapping Intervals Solution Medium 735. Asteroid Collision Solution Medium 673. Number of Longest Increasing Subsequence Solution Medium 894. All Possible Full Binary Trees Solution Medium 767. Reorganize String Solution Medium 486. Predict the Winner Solution Medium 2079. Watering Plants Solution Medium 2811. Check if it is Possible to Split Array Solution Medium 74. Search a 2D Matrix Solution Medium 2616. Minimize the Maximum Difference of Pairs Solution Medium 81. Search in Rotated Sorted Array II Solution Medium 518. Coin Change II Solution Medium 1282. Group the People Given the Group Size They Belong To Solution Medium 2369. Check if There is a Valid Partition For The Array Solution Medium 86. Partition List Solution Medium 1615. Maximal Network Rank Solution Medium 97. Interleaving String Solution Medium 646. Maximum Length of Pair Chain Solution Medium 2483. Minimum Penalty for a Shop Solution Medium 2707. Extra Characters in a String Solution Medium 377. Combination Sum IV Solution Medium 1647. Minimum Deletions to Make Character Frequencies Unique Solution Medium 6. Zigzag Conversion Solution Medium 1584. Min Cost to Connect All Points Solution Medium 1631. Path With Minimum Effort Solution Medium 1658. Minimum Operations to Reduce X to Zero Solution Medium 1048. Longest String Chain Solution Medium 799. Champagne Tower Solution Medium 316. Remove Duplicate Letters Solution Medium 880. Decoded String at Index Solution Medium 50. Pow(x, n) Solution Medium 456. 132 Pattern Solution Medium 2038. Remove Colored Pieces if Both Neighbors are the Same Color Solution Medium 229. Majority Element II Solution Medium 343. Integer Break Solution Medium Solution Hard 140. Word Break II (DP + DFS) Solution Hard 41. First Missing Positive Solution Hard 732. My Calendar III Solution Hard 1335. Minimum Difficulty of a Job Schedule Solution Hard 2136. Earliest Possible Day of Full Bloom Solution Hard 1293. Shortest Path in a Grid with Obstacles Elimination Solution Hard 212. Word Search II Solution Hard 899. Orderly Queue Solution Hard 295. Find Median from Data Stream Solution Hard 587. Erect the Fence Solution Hard 224. Basic Calculator Solution Hard 1235. Maximum Profit in Job Scheduling Solution Hard 446. Arithmetic Slices II - Subsequence Solution Hard 834. Sum of Distances in Tree Solution Hard 980. Unique Paths III Solution Hard 149. Max Points on a Line Solution Hard 2246. Longest Path With Different Adjacent Characters Solution Hard 2306. Naming a Company Solution Hard 72. Edit Distance Solution Hard 2444. Count Subarrays With Fixed Bounds Solution Hard 1345. Jump Game IV Solution Hard 23. Merge k Sorted Lists Solution Hard 1857. Largest Color Value in a Directed Graph Solution Hard 879. Profitable Schemes Solution Hard 839. Similar String Groups Solution Hard 1697. Checking Existence of Edge Length Limited Paths Solution Hard 135. Candy Solution Hard 1799. Maximize Score After N Operations Solution Hard 1721. Swapping Nodes in a Linked List(LINKED_LIST) Solution Hard 124. Binary Tree Maximum Path Sum Solution Hard 1406. Stone Game III Solution Hard 1547. Minimum Cost to Cut a Stick Solution Hard 1569. Number of Ways to Reorder Array to Get Same BST Solution Hard 1187. Make Array Strictly Increasing Solution Hard 2448. Minimum Cost to Make Array Equal Solution Hard 956. Tallest Billboard Solution Hard 1575. Count All Possible Routes Solution Hard 864. Shortest Path to Get All Keys Solution Hard 1970. Last Day Where You Can Still Cross Solution Hard 1601. Maximum Number of Achievable Transfer Requests Solution Hard 2551. Put Marbles in Bags Solution Hard 2272. Substring With Largest Variance Solution Hard 1751. Maximum Number of Events That Can Be Attended II Solution Hard 1125. Smallest Sufficient Team Solution Hard 2141. Maximum Running Time of N Computers Solution Hard 664. Strange Printer Solution Hard 920. Number of Music Playlists Solution Hard 239. Sliding Window Maximum Solution Hard 68. Text Justification Solution Hard 403. Frog Jump Solution Hard 2366. Minimum Replacements to Sort the Array Solution Hard 1326. Minimum Number of Taps to Open to Water a Garden Solution Hard 1359. Count All Valid Pickup and Delivery Options Solution Hard 332. Reconstruct Itinerary Solution Hard 847. Shortest Path Visiting All Nodes Solution Hard 4. Median of Two Sorted Arrays Solution Hard Solution