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LeetCode Problems' Solutions

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English | 简体中文

This is my personal record of solving LeetCode Problems. The algorithms may not be optimal, I hope you can understand.

If you have any questions or advices, please discuss them in Issues.

Algorithm

# Title Solution Difficulty Related Topics
1774 Closest Dessert Cost Python3 Medium Greedy
1773 Count Items Matching a Rule Python3 Easy Array, String
1758 Minimum Changes To Make Alternating Binary String Python3 Easy Greedy, Array
1752 Check if Array Is Sorted and Rotated Python3 Easy Array
1748 Sum of Unique Elements Python3 Easy Array, Hash Table
1742 Maximum Number of Balls in a Box Python3 Easy Array
1736 Latest Time by Replacing Hidden Digits Python3 Easy Greedy, String
1732 Find the Highest Altitude Python3 Easy Array
1725 Number Of Rectangles That Can Form The Largest Square Python3 Easy Greedy
1720 Decode XORed Array Python3 Easy Bit Manipulation
1716 Calculate Money in Leetcode Bank Python3 Easy Greedy, Math
1710 Maximum Units on a Truck Python3 Easy Greedy, Sort
1704 Determine if String Halves Are Alike Python3 Easy String
1700 Number of Students Unable to Eat Lunch Python3 Easy Array
1694 Reformat Phone Number Python3 Easy String
1688 Count of Matches in Tournament Python3 Easy Backtracking
1684 Count the Number of Consistent Strings Python3 Easy String
1678 Goal Parser Interpretation Python3 Easy String
1672 Richest Customer Wealth Python3 Easy Array
1668 Maximum Repeating Substring Python3 Easy String
1662 Check If Two String Arrays are Equivalent Python3 Easy String
1656 Design an Ordered Stream Python3 Easy Design, Array
1652 Defuse the Bomb Python3 Easy Array
1646 Get Maximum in Generated Array Python3 Easy Array
1640 Check Array Formation Through Concatenation Python3 Easy Sort, Array, Hash Table
1636 Sort Array by Increasing Frequency Python3 Easy Sort, Array
1629 Slowest Key Python3 Easy Array
1624 Largest Substring Between Two Equal Characters Python3 Easy String
1619 Mean of Array After Removing Some Elements Python3 Easy Array
1614 Maximum Nesting Depth of the Parentheses Python3 Easy String
1608 Special Array With X Elements Greater Than or Equal X Python3 Easy Array
1603 Design Parking System Python3 Easy Design
1598 Crawler Log Folder Python3 Easy Stack
1592 Rearrange Spaces Between Words Python3 Easy String
1588 Sum of All Odd Length Subarrays Python3 Easy Array
1582 Special Positions in a Binary Matrix Python3 Easy Array
1576 Replace All ?'s to Avoid Consecutive Repeating Characters Python3 Easy String
1572 Matrix Diagonal Sum Python3 Easy Array
1566 Detect Pattern of Length M Repeated K or More Times Python3 Easy Array
1560 Most Visited Sector in a Circular Track Python3 Easy Array
1556 Thousand Separator Python3 Easy String
1550 Three Consecutive Odds Python3 Easy Array
1544 Make The String Great Python3 Easy Stack, String
1539 Kth Missing Positive Number Python3 Easy Array, Hash Table
1534 Count Good Triplets Python3 Easy Array
1528 Shuffle String Python3 Easy Sort
1523 Count Odd Numbers in an Interval Range Python3 Easy Math
1518 Water Bottles Python3 Easy Greedy
1512 Number of Good Pairs Python3 Easy Array, Hash Table, Math
1507 Reformat Date Python3 Easy String
1502 Can Make Arithmetic Progression From Sequence Python3 Easy Sort, Array
1496 Path Crossing Python3 Easy String
1491 Average Salary Excluding the Minimum and Maximum Salary Python3 Easy Sort, Array
1486 XOR Operation in an Array Python3 Easy Bit Manipulation, Array
1480 Running Sum of 1d Array Python3 Easy Array
1475 Final Prices With a Special Discount in a Shop Python3 Easy Array
1470 Shuffle the Array Python3 Easy Array
1464 Maximum Product of Two Elements in an Array Python3 Easy Array
1460 Make Two Arrays Equal by Reversing Sub-arrays Python3 Easy Array
1455 Check If a Word Occurs As a Prefix of Any Word in a Sentence Python3 Easy String
1450 Number of Students Doing Homework at a Given Time Python3 Easy Array
1446 Consecutive Characters Python3 Easy String
1441 Build an Array With Stack Operations Python3 Easy Stack
1436 Destination City Python3 Easy String
1431 Kids With the Greatest Number of Candies Python3 Easy Array
1422 Maximum Score After Splitting a String Python3 Easy String
1417 Reformat The String Python3 Easy String
1413 Minimum Value to Get Positive Step by Step Sum Python3 Easy Array
1408 String Matching in an Array Python3 Easy String
1403 Minimum Subsequence in Non-Increasing Order Python3 Easy Greedy, Sort
1399 Count Largest Group Python3 Easy Array
1394 Find Lucky Integer in an Array Python3 Easy Array
1389 Create Target Array in the Given Order Python3 Easy Array
1385 Find the Distance Value Between Two Arrays Python3 Easy Array
1380 Lucky Numbers in a Matrix Python3 Easy Array
1374 Generate a String With Characters That Have Odd Counts Python3 Easy String
1370 Increasing Decreasing String Python3 Easy Sort, String
1365 How Many Numbers Are Smaller Than the Current Number Python3 Easy Array, Hash Table
1360 Number of Days Between Two Dates Python3 Easy None
1356 Sort Integers by The Number of 1 Bits Python3 Easy Sort, Bit Manipulation
1351 Count Negative Numbers in a Sorted Matrix Python3 Easy Array, Binary Search
1346 Check If and Its Double Exist Python3 Easy Array
1342 Number of Steps to Reduce a Number to Zero Python3 Easy Bit Manipulation
1337 The K Weakest Rows in a Matrix Python3 Easy Array, Binary Search
1332 Remove Palindromic Subsequences Python3 Easy String
1331 Rank Transform of an Array Python3 Easy Array
1323 Maximum 69 Number Python3 Easy Math
1317 Convert Integer to the Sum of Two No-Zero Integers Python3 Easy Math
1313 Decompress Run-Length Encoded List Python3 Easy Array
1309 Decrypt String from Alphabet to Integer Mapping Python3 Easy String
1304 Find N Unique Integers Sum up to Zero Python3 Easy Array
1299 Replace Elements with Greatest Element on Right Side Python3 Easy Array
1295 Find Numbers with Even Number of Digits Python3 Easy Array
1290 Convert Binary Number in a Linked List to Integer Python3 Easy Bit Manipulation, Linked List
1287 Element Appearing More Than 25% In Sorted Array Python3 Easy Array
1281 Subtract the Product and Sum of Digits of an Integer Python3 Easy Math
1275 Find Winner on a Tic Tac Toe Game Python3 Easy Array
1266 Minimum Time Visiting All Points Python3 Easy Geometry, Array
1260 Shift 2D Grid Python3 Easy Array
1252 Cells with Odd Values in a Matrix Python3 Easy Array
1237 Find Positive Integer Solution for a Given Equation Python3 Easy Math, Binary Search
1232 Check If It a Straight Line Python3 Easy Geometry, Array, Math
1221 Split a String in Balanced Strings Python3 Easy Greedy, String
1217 Minimum Cost to Move Chips to The Same Position Python3 Easy Greedy, Array, Math
1207 Unique Number of Occurrences Python3 Easy Hash Table
1200 Minimum Absolute Difference Python3 Easy Array
1189 Maximum Number of Balloons Python3 Easy Hash Table, String
1185 Day of the Week Python3 Easy Array
1184 Distance Between Bus Stops Python3 Easy Array
1175 Prime Arrangements Python3 Easy Math
1170 Compare Strings by Frequency of the Smallest Character Python3 Easy Array, String
1160 Find Words That Can Be Formed by Characters Python3 Easy Array, Hash Table
1154 Day of the Year Python3 Easy Math
1137 N-th Tribonacci Number Python3 Easy Recursion
1128 Number of Equivalent Domino Pairs Python3 Easy Array
1122 Relative Sort Array Python3 Easy Sort, Array
1108 Defanging an IP Address Python3 Easy String
1103 Distribute Candies to People Python3 Easy Math
1089 Duplicate Zeros Python3 Easy Array
1078 Occurrences After Bigram Python3 Easy Hash Table
1071 Greatest Common Divisor of Strings Python3 Easy String
1051 Height Checker Python3 Easy Array
1047 Remove All Adjacent Duplicates In String Python3 Easy Stack
1046 Last Stone Weight Python3 Easy Heap, Greedy
1037 Valid Boomerang Python3 Easy Math
1033 Moving Stones Until Consecutive Python3 Easy Brainteaser
1030 Matrix Cells in Distance Order Python3 Easy Sort
1025 Divisor Game Python3 Easy Math, Dynamic Programming
1022 Sum of Root To Leaf Binary Numbers Python3 Easy Tree
1021 Remove Outermost Parentheses Python3 Easy Stack
1018 Binary Prefix Divisible by 5 Python3 Easy Array
1013 Partition Array Into Three Parts With Equal Sum Python3 Easy Array
1010 Pairs of Songs With Total Durations Divisible by 60 Python3 Easy Array
1009 Complement of Base 10 Integer Python3 Easy Math
1005 Maximize Sum of Array After K Negations Python3 Easy Greedy
1002 Find Common Characters Python3 Easy Array, Hash Table
999 Available Captures for Rook Python3 Easy Array
997 Find the Town Judge Python3 Easy Graph
993 Cousins in Binary Tree Python3 Easy Tree, Breadth-first Search
989 Add to Array-Form of Integer Python3 Easy Array
985 Sum of Even Numbers After Queries Python3 Easy Array
977 Squares of a Sorted Array Python3 Easy Array, Two Pointers
976 Largest Perimeter Triangle Python3 Easy Sort, Math
970 Powerful Integers Python3 Easy Hash Table, Math
965 Univalued Binary Tree Python3 Easy Tree
961 N-repeated Element in Size 2N Array Python3 Easy Hash Table
953 Verifying an Alien Dictionary Python3 Easy Hash Table
944 Delete Columns to Make Sorted Python3 Easy Greedy
942 DI String Match Python3 Easy Math
941 Valid Mountain Array Python3 Easy Array
938 Range Sum of BST Python3 Easy Tree, Recursion
937 Reorder Data in Log Files Python3 Easy String
933 Number of Recent Calls Python3 Easy Queue
929 Unique Email Addresses Python3 Easy String
925 Long Pressed Name Python3 Easy Two Pointers, String
922 Sort Array By Parity II Python3 Easy Sort, Array
917 Reverse Only Letters Python3 Easy String
914 X of a Kind in a Deck of Cards Python3 Easy Array, Math
908 Smallest Range I Python3 Easy Math
905 Sort Array by Parity Python3 Easy Array
897 Increasing Order Search Tree Python3 Easy Tree, Depth-first Search
896 Monotonic Array Python3 Easy Array
893 Groups of Special-Equivalent Strings Python3 Easy String
892 Surface Area of 3D Shapes Python3 Easy Geometry, Math
888 Fair Candy Swap Python3 Easy Array
884 Uncommon Words from Two Sentences Python3 Easy Hash Table
883 Projection Area of 3D shapes Python3 Easy Math
876 Middle of the Linked List Python3 Easy Linked List
874 Walking Robot Simulation Python3 Easy Greedy
872 Leaf-Similar Tree Python3 Easy Tree, Depth-first Search
868 Binary Gap Python3 Easy Math
867 Transpose Matrix Python3 Easy Array
860 Lemonade Change Python3 Easy Greedy
859 Buddy Strings Python3 Easy String
852 Peak Index in a Mountain Array Python3 Easy Binary Search
844 Backspace String Compare Python3 Easy Stack, Two Pointers
836 Rectangle Overlap Python3 Easy Math
832 Flipping an Image Python3 Easy Array
830 Position of Large Groups Python3 Easy Array
824 Goat Latin Python3 Easy String
821 Shortest Distance to a Character Python3 Easy None
819 Most Common Word Python3 Easy String
812 Largest Triangle Area Python3 Easy Math
811 Subdomain Visit Count Python3 Easy Hash Table
806 Number of Lines To Write String Python3 Easy None
804 Unique Morse Code Words Python3 Easy String
796 Rotate String Python3 Easy None
788 Rotated Digits Python3 Easy String
783 Minimum Distance Between BST Nodes Python3 Easy Tree, Recursion
771 Jewels and Stones Python3 Easy Hash Table
766 Toeplitz Matrix Python3 Easy Array
762 Prime Number of Set Bits in Binary Representation Python3 Easy Bit Manipulation
748 Shortest Completing Word Python3 Easy Hash Table
747 Largest Number At Least Twice of Others Python3 Easy Array
746 Min Cost Climbing Stairs Python3 Easy Array, Dynamic Programming
744 Find Smallest Letter Greater Than Target Python3 Easy Binary Search
733 Flood Fill Python3 Easy Depth-first Search
728 Self Dividing Numbers Python3 Easy Math
724 Find Pivot Index Python3 Easy Array
720 Longest Word in Dictionary Python3 Easy Trie, Hash Table
717 1-bit and 2-bit Characters Python3 Easy Array
709 To Lower Case Python3 Easy String
706 Design HashMap Python3 Easy Design, Hash Table
705 Design HashSet Python3 Easy Design, Hash Table
704 Binary Search Python3 Easy Binary Search
703 Kth Largest Element in a Stream Python3 Easy Heap
700 Search in a Binary Search Tree Python3 Easy Tree
697 Degree of an Array Python3 Easy Array
696 Count Binary Substrings Python3 Easy String
693 Binary Number with Alternating bits Python3 Easy Bit Manipulation
690 Employee Importance Python3 Easy Depth-first Search, Breadth-first Search, Hash Table
687 Longest Univalue Path Python3 Easy Tree, Recursion
686 Repeated String Match Python3 Easy String
682 Baseball Game Python3 Easy Stack
680 Valid Palindrome II Python3 Easy String
674 Longest Continuous Increasing Subsequence Python3 Easy Array
671 Second Minimum Node in a Binary Tree Python3 Easy Tree
669 Trim a Binary Search Tree Python3 Easy Tree
665 Non-decreasing Array Python3 Easy Array
661 Image Smoother Python3 Easy Array
657 Robot Return to Origin Python3 Easy String
653 Two Sum IV - Input is a BST Python3 Easy Tree
645 Set Mismatch Python3 Easy Hash Table, Math
643 Maximum Average Subarray I Python3 Easy Array
637 Average of Levels in Binary Tree Python3 Easy Tree
633 Sum of Square Numbers Python3 Easy Math
628 Maximum Product of Three Numbers Python3 Easy Array, Math
621 Task Scheduler Java 中等 贪心, 数组, 哈希表, 计数, 排序, 堆(优先队列)
617 Merge Two Binary Trees Python3 Easy Tree
606 Construct String from Binary Tree Python3 Easy Tree, String
605 Can Place Flowers Python3 Easy Array
599 Minimum Index Sum of Two Lists Python3 Easy Hash Table
598 Range Addition II Python3 Easy Math
594 Longest Harmonious Subsequence Python3 Easy Hash Table
590 N-ary Tree Postorder Traversal Python3 Easy Tree
589 N-ary Tree Preorder Traversal Python3 Easy Tree
581 Shortest Unsorted Continuous Subarray Python3 Easy Array
575 Distribute Candies Python3 Easy Hash Table
572 Subtree of Another Tree Python3 Easy Tree
566 Reshape the Matrix Python3 Easy Array
563 Binary Tree Tilt Python3 Easy Tree
561 Array Partition I Python3 Easy Array
559 Maximum Depth of N-ary Tree Python3 Easy Tree, Depth-first Search, Breadth-first Search
557 Reverse Words in a String III Python3 Easy String
551 Student Attendance Record I Python3 Easy Tree
543 Diameter of Binary Tree Python3 Easy Tree
541 Reverse String II Python3 Easy String
538 Convert BST to Greater Tree Python3 Easy Tree
532 K-diff Pairs in an Array Python3 Easy Array, Two Pointers
530 Minimum Absolute Difference in BST Python3 Easy Tree
521 Longest Uncommon Subsequence I Python3 Easy String
520 Detect Capital Python3 Easy String
509 Fibonacci Number Python3 Easy Array
507 Perfect Number Python3 Easy Math
506 Relative Ranks Python3 Easy None
504 Base 7 Python3 Easy None
501 Find Mode in Binary Search Tree Python3 Easy Tree
500 Keyboard Row Python3 Easy Hash Table
496 Next Greater Element I Python3 Easy Stack
492 Construct the Rectangle Python3 Easy None
485 Max Consecutive Ones Python3 Easy Array
482 License Key Formatting Python3 Easy None
476 Number Complement Python3 Easy Bit Manipulation
475 Heaters Python3 Easy Binary Search
463 Island Perimeter Python3 Easy Hash Table
461 Hamming Distance Python3, Java Easy Bit Manipulation
459 Repeated Substring Pattern Python3 Easy String
455 Assign Cookies Python3 Easy Greedy
453 Minimum Moves to Equal Array Elements Python3 Easy Math
448 Find All Numbers Disappeared in an Array Python3 Easy Array
447 Number of Boomerangs Python3 Easy Hash Table
443 String Compression Python3 Easy String
441 Arranging Coins Python3 Easy Math, Binary Search
437 Path Sum III Python3 Easy Tree
434 Number of Segments in a String Python3 Easy String
415 Add Strings Python3 Easy String
414 Third Maximum Number Python3 Easy Array
412 Fizz Buzz Python3, Java Easy None
409 Longest Palindrome Python3 Easy Hash Table
405 Convert a Number to Hexadecimal Python3 Easy Bit Manipulation
403 Sum of Left Leaves Python3 Easy Tree
401 Binary Watch Python3 Easy Bit Manipulation, Backtracking
392 Is Subsequence Python3 Easy Greedy, Binary Search, Dynamic Programming
389 Find the Difference Python3 Easy Bit Manipulation, Hash Table
387 First Unique CHaracter in a String Python3, Java Easy Hash Table, String
384 Shuffle an Array Java Medium Array, Math, Randomized
383 Ransom Note Python3 Easy String
380 Insert Delete GetRandom O(1) Java Medium Design, Array, Hash Table, Math, Randomized
374 Guess Number Higher or Lower Python3 Easy Binary Search
371 Sum of Two Integers Python3 Easy Bit Manipulation
367 Valid Perfect Square Python3 Easy Math, Binary Search
350 Intersection of Two Arrays II Python3, Java Easy Sort, Hash Table, Two Pointers, Binary Search
349 Intersection of Two Arrays Python3 Easy Sort, Hash Table, Two Pointers, Binary Search
347 Top K Frequent Elements Java Medium Array, Hash Table, Divide and Conquer, Bucket Sort, Counting, Quickselect, Sorting, Heap(Priority Queue)
345 Reverse Vowels of a String Python3 Easy Two Pointers, String
344 Reverse String Python3, Java Easy Two Pointers, String
342 Power of Four Python3 Easy Bit Manipulation
334 Increasing Triplet Subsequence Java Medium Greedy, Array
328 Odd Even Linked List Java Medium Linked List
326 Power of Three Python3, Java Easy Math
322 Coin Change Java Medium Breadth-First, Array, Dynamic Programming
303 Range Sum Query - Immutable Python3 Easy Dynamic Programming
300 Longest Increasing Subsequence Java Medium Array, Binary Search, Dynamic Programming
299 Bulls and Cows Python3 Easy Hash Table
292 Nim Game Python3 Easy Brainteaser, Minimax
297 Serialize and Deserialize Binary Tree Java Hard Tree, Depth-First Search, Breadth-First Search, Design, String, Binary Tree
290 Word Pattern Python3 Easy Hash Table
283 Move Zeroes Python3, Java Easy Array, Two Pointers
278 First Bad Version Python3, Java Easy Binary Search
268 Missing Number Python3, Java Easy Bit Manipulation, Array, Math
263 Ugly Number Python3 Easy Math
258 Add Digits Python3 Easy Math
257 Binary Tree Paths Python3 Easy Tree, Depth-first Search
242 Valid Anagram Python3, Java Easy Sort, Hash Table
240 Search a 2D Matrix II Java Medium Array, Binary Search, Divide and Conquer, Matrix
237 Delete Node in a Linked List Python3, Java Easy Linked List
235 Lowest Common Ancestor of a Binary Search Tree Python3 Easy Tree
234 Palindrome Linked List Python3, Java Easy Linked List, Two Pointers
232 Implement Queue using Stacks Python3 Easy Stack, Design
231 Power of Two Python3 Easy Bit Manipulation, Math
230 Kth Smallest Element in a BST Java Medium Tree, Depth-First Search, Binary Search Tree, Binary Tree
228 Summary Ranges Python3 Easy Array
226 Invert Binary Tree Python3 Easy Tree
225 Implement Stack using Queues Python3 Easy Stack, Design
219 Contains Duplicate II Python3 Easy Array, Hash Table
217 Contains Duplicate Python3, Java Easy Array, Hash Table
215 Kth Largest Element in an Array Java Medium Array, Divide and Conquer, Quickselect, Sorting, Heap(Priority Queue)
206 Reverse Linked List Python3, Java Easy Linked List
205 Isomorphic Strings Python3 Easy Hash Table
204 Count Primes Python3, Java Easy Hash Table, Math
203 Remove Linked List Elements Python3 Easy Linked List
202 Happy Number Python3, Java Easy Hash Table, Math
200 Number of Islands Java Medium Depth-First Search, Breadth-First Search, Union Find, Array, Matrix
198 House Robber Python3, Java Easy Dynamic Programming
191 Number of 1 Bits Python3, Java Easy Bit Manipulation
190 Reverse Bits Python3, Java Easy Bit Manipulation
189 Rotate Array Python3, Java Easy Array
187 Repeated DNA Sequences Python3 Medium Bit Manipulation, Hash Table, String, Sliding Windows, Hash Function, Rolling Hash
179 Largest Number Python3 Medium Greedy, String, Sorting
173 Binary Search Tree Iterator Python3 Medium Stack, Tree, Design, Binary Search Tree, Binary Tree, Iterator
172 Factorial Trailing Zeroes Python3, Java Easy Math
171 Excel Sheet Column Number Python3, Java Easy Math
169 Majority Element Python3, Java Easy Bit Manipulation, Array, Divide and Conquer
168 Excel Sheet Column Title Python3 Easy Math
167 Two Sum II - Input Array is Sorted Python3 Easy Array, Two Pointers, Binary Search
166 Fraction to Recurring Decimal Python3 Medium Hash Table, Math, String
165 Compare Version Numbers Python3 Medium String
162 Find Peak Element Python3, Java Medium Array, Binary Search
160 Intersection of Two Linked Lists Python3, Java Easy Linked List
155 Min Stack Python3, Java Easy Stack, Design
153 Find Minimum in Rotated Sorted Array Python3 Medium Array, Binary Search
152 Maximum Product Subarray Python3 Medium Array, Dynamic Programming
151 Reverse Words in a String Python3 Medium String
150 Evaluate Reverse Polish Notation Python3 Medium Stack
148 Sort List Python3 Medium Sort, Linked List
147 Insertion Sort List Python3 Medium Sort, Linked List
146 LRU Cache Python3 Medium Design
144 Binary Tree Preorder Traversal Python3 Medium Stack, Tree
143 Reorder List Python3 Medium Linked List
142 Linked List Cycle II Python3 Medium Linked List, Two Pointers
141 Linked List Cycle Python3, Java Easy Linked List, Two Pointers
139 Word Break Python3 Medium Dynamic Programming
138 Copy List with Random Pointer Python3 Medium Hash Table, Linked List
137 Single Number II Python3 Medium Bit Manipulation
136 Single Number Python3, Java Easy Bit Manipulation, Hash Table
134 Gas Station Python3 Medium Greedy
133 Clone Graph Python3 Medium Depth-first Search, Breadth-first Search, Graph
131 Palindrome Partitioning Python3 Medium Depth-first Search, Dynamic Programming, Backtracking
130 Surrounded Regions Python3 Medium Depth-first Search, Breadth-first Search, Union Find
129 Sum Root to Leaf Numbers Python3 Medium Tree, Depth-first Search
128 Longest Consecutive Sequence Python3 Medium Union Find, Array
125 Valid Palindrome Python3, Java Easy Two Pointers, String
122 Best Time to Buy and Sell Stock II Python3, Java Easy Greedy, Array
121 Best Time to Buy and Sell Stock Python3, Java Easy Array, Dynamic Programming
120 Triangle Python3 Medium Array, Dynamic Programming
119 Pascal's Triangle II Python3 Easy Array
118 Pascal's Triangle Python3, Java Easy Array
117 Populating Next Right Pointers in Each Node Python3 Medium Tree, Depth-first Search
116 Populating Next Right Pointers in Each Node Python3, Java Medium Tree, Depth-first Search, Breadth-first Search
114 Flatten Binary Tree to Linked List Python3 Medium Tree, Depth-first Search
113 Path Sum II Python3 Medium Tree, Depth-first Search
112 Path Sum Python3 Easy Tree, Depth-first Search
111 Minimum Depth of Binary Tree Python3 Easy Tree, Depth-first Search, Breadth-first Search
110 Balanced Binary Tree Python3 Easy Tree, Depth-first Search
109 Convert Sorted List to Binary Search Tree Python3 Medium Depth-first Search, Linked List
108 Convert Sorted Array to Binary Search Tree Python3, Java Easy Tree, Depth-first Search
107 Binary Tree Level Order Traversal II Python3 Easy Tree, Breadth-first Search
106 Construct Binary Tree from Inorder and Postorder Traversal Python3 Medium Tree, Depth-first Search, Array
105 Construct Binary Tree from Preorder and Inorder Traversal Python3, Java Medium Tree, Depth-first Search, Array
104 Maximum Depth of Binary Tree Python3, Java Easy Tree, Depth-first Search
103 Binary Tree Zigzag Level Order Traversal Java Medium Tree, Breadth-First Search, Binary Tree
102 Binary Tree Level Order Traversal Python3, Java Medium Tree, Breadth-first Search
101 Symmetric Tree Python3, Java Easy Tree, Depth-first Search, Breadth-first Search
100 Same Tree Python3 Easy Tree, Depth-first Search
98 Validate Binary Search Tree Python3, Java Medium Tree, Depth-first Search, Recursion
97 Interleaving String Python3 Medium String, Dynamic Programming
96 Unique Binary Search Trees Python3 Medium Tree, Dynamic Programming
95 Unique Binary Search Trees II Python3 Medium Tree, Dynamic Programming
94 Binary Tree Inorder Traversal Python3, Java Medium Stack, Tree, Hash Table
93 Restore IP Addresses Python3 Medium String, Backtracking
92 Reverse Linked List II Python3 Medium Linked List
91 Decode Ways Python3 Medium String, Dynamic Programming
90 Subsets II Python3 Medium Array, Backtracking
89 Gray Code Python3 Medium Backtracking
88 Merge Sorted Array Python3, Java Easy Array, Two Pointers
86 Partition List Python3 Medium Linked List, Two Pointers
83 Remove Duplicates from Sorted List Python3 Easy Linked List
82 Remove Duplicates from Sorted List II Python3 Medium Linked List
81 Search in Rotated Sorted Array II Python3 Medium Array, Binary Search
80 Remove Duplicates from Sorted Array II Python3 Medium Array, Two Pointers
79 Word Search Python3, Java Medium Array, Backtracking
78 Subsets Python3, Java Medium Bit Manipulation, Array, Backtracking
77 Combinations Python3 Medium Backtracking
75 Sort Colors Python3, Java Medium Sort, Array, Two Pointers
74 Search a 2D Matrix Python3 Medium Array, Binary Search
73 Set Matrix Zeroes Python3, Java Medium Array
71 Simplify Path Python3 Medium Stack, String
70 Climbing Stairs Python3, Java Easy Dynamic Programming
69 Sqrt(x) Python3, Java Easy Math, Binary Search
67 Add Binary Python3 Easy Math, String
66 Plus One Python3, Java Easy Array
64 Minimum Path Sum Python3 Medium Array, Dynamic Programming
63 Unique Paths II Python3 Medium Array, Dynamic Programming
62 Unique Paths Python3, Java Medium Array, Dynamic Programming
61 Rotate List Python3 Medium Linked List, Two Pointers
59 Spiral Matrix II Python3 Medium Array
58 Length of Last Word Python3 Easy String
57 Insert Interval Python3 Medium Sort, Array
56 Merge Intervals Python3, Java Medium Sort, Array
55 Jump Game Python3, Java Medium Greedy, Array
54 Spiral Matrix Python3 Medium Array
53 Maximum Subarray Python3, Java Easy Array, Divide and Conquer, Dynamic Programming
50 Pow(x, n) Python3, Java Medium Math, Binary Search
49 Group Anagrams Python3, Java Medium Hash Table, String
48 Rotate Image Python3, Java Medium Array
47 Permutations II Python3 Medium Backtracking
46 Permutations Python3, Java Medium Backtracking
45 Jump Game II Python3 Medium Greedy, Array
43 Multiply Strings Python3 Medium Math, String
40 Combination Sum II Python3 Medium Array, Backtracking
39 Combination Sum Python3 Medium Array, Backtracking
38 Count And Say Python3, Java Easy String
36 Valid Sudoku Python3, Java Medium Hash Table
35 Search Insert Position Python3 Easy Array, Binary Search
34 Find First and Last Position of Element in Sorted Array Python3, Java Medium Array, Binary Search
33 Search in Rotated Sorted Array Python3, Java Medium Array, Binary Search
31 Next Permutation Python3 Medium Array
29 Divide Two Integers Python3, Java Medium Math, Binary Search
28 Implement strStr() Python3, Java Easy Two Pointers, String
27 Remove Element Python3 Easy Array, Two Pointers
26 Remove Duplicates From Sorted Array Python3, Java Easy Array, Two Pointers
24 Swap Nodes in Pairs Python3 Medium Recursion, Linked List
22 Generate Parentheses Python3, Java Medium String, Backtracking
21 Merge Two Sorted Lists Python3, Java Easy Linked List
20 Valid Parentheses Python3, Java Easy Stack, String
19 Remove Nth Node From End of List Python3, Java Medium Linked List, Two Pointers
18 4Sum Python3 Medium Array, Hash Table, Two Pointers
17 Letter Combinations of a Phone Number Python3, Java Medium Depth-first Search, Recursion, String, Backtracking
16 3Sum Closest Python3 Medium Array, Two Pointers
15 3Sum Python3, Java Medium Array, Two Pointers
14 Longest Common Prefix Python3, Java Easy String
13 Roman to Integer Python3, Java Easy Math, String
12 Integer to Roman Python3 Medium Math, String
11 Container With Most Water Python3 Medium Array, Two Pointers
9 Palindrome Number Python3 Easy Math
8 String to Integer (atoi) Python3, Java Medium Math, String
7 Reverse Integer Python3, Java Easy Math
6 Zigzag Conversion Python3 Medium String
5 Longest Palindromic Substring Python3, Java Medium String, Dynamic Programming
3 Longest Substring Without Repeating Characters Python3, Java Medium Hash Table, Two Pointers, String, Sliding Window
2 Add Two Numbers Python3, Java Medium Recursion, Linked List, Math
1 Two Sum Python3, Java Easy Array, Hash Table

Database

# Title Solution Difficulty
1179 Reformat Department Table MySQL Easy
627 Swap Salary MySQL Easy
620 Not Boring Movies MySQL Easy
596 Classes More Than 5 Students MySQL Easy
595 Big Countries MySQL Easy
197 Rising Temperature MySQL Easy
196 Delete Duplicate Emails MySQL Easy
184 Department Highest Salary MySQL Medium
183 Customer Who Never Order MySQL Easy
182 Duplicate Emails MySQL Easy
181 Employees Earning More Than Their Managers MySQL Easy
180 Consecutive Numbers MySQL Medium
178 Rank Scores MySQL Medium
177 Nth Highest Salary MySQL Medium
176 Second Highest Salary MySQL Easy
175 Combine Two Tables MySQL Easy

Shell

# Title Solution Difficulty
195 Tenth Line Bash Easy
194 Transpose File Bash Medium
193 Valid Phone Number Bash Easy
192 Word Frequency Bash Medium

Concurrency

# Title Solution Difficulty
1114 Print in Order Python3 Easy