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Record my training on LeetCode in my doctoral life

LeetCode Record

🐼 A daily journey of honing my programming skills and documenting my insights solutions and std solutions.

I categorize problems based on their optimal solution algorithm. If there's no fixed algorithm, I label it as a trick (requiring creativity, no template algorithm). If a problem isn't listed in the summary table, it means it's simple enough to complete during my sophomore year.

  • Scripts folder is used to store my accepted code. Feel free to copy it for submission, but I recommend reading my code and insights before writing your own solution.

    1. I use languages such as C, CPP, Python3, Java, and GO depending on my preference.

    2. Filenames with xxx_std indicate that I've used someone else's code, either because the question is easy, the implementation is straightforward (I'm feeling lazy), or the problem is too difficult. I often use grandyang's code !, and I'm grateful for his help!

  • Insights folder contains records of my insights for each problem. If you're having trouble understanding the code, refer to the corresponding insight file (note that my solutions might not always be the best).

  • Year_Month folder contains the daily challenge on LeetCode. I complete the weekday problems, and the Readme in this folder provides insights.

Valuable Problems

Hard to associate them with a fixed algorithm

  • 91 Decode Ways
  • 117 Populating Next Right Pointers in Each Node II
  • 128 Longest Consecutive Sequence
  • 141 Linked List Cycle
  • 166 Fraction to Recurring Decimal
  • 169 Majority Element
  • 177 Nth Highest Salary
  • 179 Largest Number
  • 185 Department Top Three Salaries
  • 192 Word Frequency
  • 194 Transpose File
  • 199 Binary Tree Right Side View
  • 214 Shortest Palindrome
  • 218 The Skyline Problem
  • 233 Number of Digit One
  • 239 Sliding Window Maximum
  • 240 Search a 2D Matrix II
  • 287 Find the Duplicate Number
  • 420 Strong Password Checker
  • 421 Maximum XOR of Two Numbers in an Array
  • 456 132 Pattern
  • 458 Poor Pigs
  • 472 Concatenated Words
  • 479 Largest Palindrome Product
  • 502 IPO
  • 516 Longest Palindromic Subsequence == LCS
  • 517 Super Washing Machines
  • 523 Continuous Subarray Sum
  • 542 01 Matrix
  • 546 Remove Boxes
  • 591 Tag Validator
  • 632 Smallest Range Covering Elements from K Lists
  • 1044 Longest Duplicate Substring

Template

  • Trie - 472
  • PairHash
  • Disjoint set
  • Fenwick Tree
  • Linked List Operation

Summary Table

# Title Solution Insights Difficulty
10 Regular Expression Matching CPP Recursion Hard
11 Container With Most Water CPP Trcik medium
12 Interger to Roman CPP Trcik medium
15 3Sum CPP Divide and Conquer medium
16 3Sum Closest CPP Divide and Conquer medium
18 4Sum CPP Divide and Conquer medium
22 Generate Parentheses CPP Recursion medium
23 Merge k Sorted Lists CPP Merge Hard
25 Reverse Nodes in k-Group C++ Simulation Hard
29 Divide Two Integers C++ Bit Operation Medium
30 Substring with Concatenation of All Words C++ Data Structure Hard
31 Next Permutation PY Trick Medium
32 Longest Valid Parentheses C++ DP Hard
33 Search in Rotated Sorted Array C++ Binary Search Medium
34 Find First and Last Position of Element in Sorted Array C++ Binary Search Medium
36 Valid Sudoku C++ Trick Medium
37 Sudoku Solver C++ DFS Hard
40 Combination Sum II C++ DP Medium
41 First Missing Positive C++ Bucket+Trick Hard
42 Trapping Rain Water C++ Data Structure Hard
43 Multiply Strings C++ Trick Medium
44 Wildcard Matching C++ Trick Hard
45 Jump Game II C++ DP Hard
46 Permutations C++ Trick Medium
47 Permutations II C++ Trick+Data Structure Medium
48 Rotate Image C++ Trick Medium
49 Group Anagrams C++ Data Structure Medium
50 Pow(x, n) C++ Quick Pow Medium
51 N-Queens C++ DFS Hard
52 N-Queens II C++ DFS Hard
54 Spiral Matrix C++ Trick Medium
56 Merge Intervals C++ Trick Medium
57 Insert Interval C++ Trick Medium
58 Length of Last Word C++ Trick Easy
59 Spiral Matrix II C++ Trick Medium
60 Permutation Sequence C++ DFS Hard
61 Rotate List PY Trick Medium
64 Minimum Path Sum C++ DP Medium
65 Valid Number C++ STATE MACHINE Hard
66 Plus One C++ Arbitrary-precision Arithmetic Easy
67 Add Binary PY Arbitrary-precision Arithmetic Easy
68 Text Justification C++ Trick Hard
69 Sqrt(x) C++ Trick Easy
71 Simplify Path C++ String Operations Medium
72 Edit Distance C++ DP Hard
73 Set Matrix Zeroes C++ Trick Medium
74 Search a 2D Matrix C++ Binary Search Medium
75 Sort Colors C++ Trick Medium
76 Minimum Window Substring C++ Greedy Hard
77 Combinations C++ DFS Medium
79 Word Search C++ DFS Medium
80 Remove Duplicates from Sorted Array II C++ Data Structure Medium
81 Search in Rotated Sorted Array II C++ Binary Search Medium
82 Remove Duplicates from Sorted List II C++ Linked List Operation Medium
83 Remove Duplicates from Sorted List C++ Linked List Operation Easy
84 Largest Rectangle in Histogram C++ Tricky Hard
85 Maximal Rectangle SQL Tricky Hard
86 Partition List C++ Linked List Operation Medium
87 Scramble String C++ Recursion Hard
88 Merge Sorted Array C++ Merge Sort Easy
89 Gray Code C++ Bit Operation Medium
90 Subsets II C++ DFS Medium
91 Decode Ways C++ DP Medium
92 Reverse Linked List II C++ Linked List Operation Medium
93 Restore IP Addresses C++ Brute Force Medium
94 Binary Tree Inorder Traversal C++ DFS Medium
95 Unique Binary Search Trees II C++ DFS Medium
97 Interleaving String C++ DP Hard
98 Validate Binary Search Tree C++ DFS Medium
99 Recover Binary Search Tree C++ DFS Hard
101 Symmetric Tree C++ DFS Easy
102 Binary Tree Level Order Traversal C++ DFS Medium
103 Binary Tree Zigzag Level Order Traversal C++ DFS Medium
104 Maximum Depth of Binary Tree C++ DFS Easy
105 Construct Binary Tree from Preorder and Inorder Traversal C++ Recrusion Medium
106 Construct Binary Tree from Inorder and Postorder Traversal C++ Recursion Medium
107 Binary Tree Level Order Traversal II C++ DFS Medium
108 Convert Sorted Array to Binary Search Tree C++ Recrusion Easy
109 Convert Sorted List to Binary Search Tree C++ Recursion Medium
110 Balanced Binary Tree C++ DFS Easy
111 Minimum Depth of Binary Tree C++ DFS Easy
112 Path Sum C++ DFS Easy
113 Path Sum II C++ DFS Medium
114 Flatten Binary Tree to Linked List C++ Recursion with While Medium
115 Distinct Subsequences C++ DP Hard
116 Populating Next Right Pointers in Each Node C++ Recursion Medium
117 Populating Next Right Pointers in Each Node II C++ Recursion Medium
118 Pascal's Triangle C++ DP Easy
119 Pascal's Triangle II C++ DP Easy
120 Triangle C++ DP Medium
123 Best Time to Buy and Sell Stock III C++ DP Hard
124 Binary Tree Maximum Path Sum C++ DFS Hard
126 Word Ladder II C++ Memory Based Search Hard
127 Word Ladder C++ Memory Based Search Hard
128 Longest Consecutive Sequence C++ Brute Force with Data Structure Hard
129 Sum Root to Leaf Numbers C++ DFS Medium
130 Surrounded Regions C++ DFS Medium
131 Palindrome Partitioning C++ Brute Force Medium
132 Palindrome Partitioning II C++ DP Hard
133 Clone Graph C++ Brute Force Medium
135 Candy C++ DP Hard
137 Single Number II C++ BIT OPERATION Medium
138 Copy List with Random Pointer C++ Brute Force Medium
139 Word Break PY DP Medium
140 Word Break II PY DFS Hard
141 Linked List Cycle C++ Tricky Easy
142 Linked List Cycle II C++ Tricky Medium
143 Reorder List C++ Simulation Medium
144 Binary Tree Preorder Traversal C++ DFS Medium
145 Binary Tree Postorder Traversal C++ DFS Medium
146 LRU Cache C++ Data Structure Medium
147 Insertion Sort List C++ Simulation Medium
149 Max Points on a Line C++ Tricky Hard
150 Evaluate Reverse Polish Notation C++ Data Structure Medium
151 Reverse Words in a String PYs Simulation Medium
152 Maximum Product Subarray C++ DP Medium
153 Find Minimum in Rotated Sorted Array C++ Binary Search Medium
154 Find Minimum in Rotated Sorted Array II C++ Binary Search Hard
155 Min Stack C++ Data Structure Easy
160 Intersection of Two Linked Lists C++ Linked List Operation Easy
162 Find Peak Element C++ Binary Search Medium
164 Maximum Gap C++ Tricky Hard
165 Compare Version Numbers C++ Data Structure Medium
166 Fraction to Recurring Decimal C++ Tricky Medium
167 Two Sum II - Input array is sorted C++ Binary Search Easy
168 Excel Sheet Column Title C++ Simulation Easy
169 Majority Element C++ Tricky Easy
171 Excel Sheet Column Number C++ Simulation Easy
172 Factorial Trailing Zeroes C++ Tricky Easy
173 Binary Search Tree Iterator C++ DFS Medium
174 Dungeon Game C++ DP Hard
175 Combine Two Tables SQL SQL Easy
176 Second Highest Salary SQL SQL Easy
177 Nth Highest Salary SQL SQL Medium
178 Rank Scores SQL SQL Medium
179 Largest Number C++ Recurssion Medium
180 Consecutive Numbers SQL SQL Medium
181 Employees Earning More Than Their Managers SQL SQL Easy
182 Duplicate Emails SQL SQL Easy
183 Customers Who Never Order SQL SQL Easy
184 Department Highest Salary SQL SQL Medium
185 Department Top Three Salaries SQL SQL Hard
187 Repeated DNA Sequences C++ Data Structure Medium
188 Best Time to Buy and Sell Stock IV C++ DP Hard
189 Rotate Array C++ Simulation Medium
190 Reverse Bits C++ Bit Operation Easy
191 Number of 1 Bits C++ Bit Operations Easy
192 Word Frequency SH Linux Medium
193 Valid Phone Numbers SH Linux Easy
194 Transpose File SH Linux Medium
195 Tenth Line SH Linux Easy
196 Delete Duplicate Emails SQL SQL Easy
197 Rising Temperature SQL SQL Easy
199 Binary Tree Right Side View C++ Tricky Medium
200 Number of Islands C++ DFS Medium
201 Bitwise AND of Numbers Range C++ Bit Operations Medium
202 Happy Number C++ Simulation Easy
203 Remove Linked List Elements C++ Linked List Operations Easy
204 Count Primes C++ Tricky Easy
205 Isomorphic Strings C++ Simulation Easy
206 Reverse Linked List C++ Linked List Operations Easy
207 Course Schedule C++ DFS Medium
208 Implement Trie (Prefix Tree) C++ Data Structure Medium
209 Minimum Size Subarray Sum C++ Tricky Medium
210 Course Schedule II C++ Brute Force Medium
212 Word Search II C++ Data Structure Hard
214 Shortest Palindrome C++ Recursion Hard
215 Kth Largest Element in an Array C++ Simulation Medium
217 Contains Duplicate C++ Data Structure Easy
218 The Skyline Problem C++ Simulation Hard
219 Contains Duplicate II C++ Data Structure Easy
221 Maximal Square C++ DP Medium
222 Count Complete Tree Nodes C++ Recursion Medium
223 Rectangle Area C++ Tricky Medium
224 Basic Calculator PY Stack Hard
225 Implement Stack using Queues C++ Data Structure Easy
226 Invert Binary Tree C++ Recursion Easy
227 Basic Calculator II C++ Stack Medium
230 Kth Smallest Element in a BST C++ DFS Medium
231 Power of Two C++ Simulation Easy
232 Implement Queue using Stacks C++ Data Structure Easy
233 Number of Digit One C++ Tricky Hard
234 Palindrome Linked List C++ Linked List Operation Easy
235 Lowest Common Ancestor of a Binary Search Tree C++ Recursion Easy
236 Lowest Common Ancestor of a Binary Tree C++ Recursion Medium
237 Delete Node in a Linked List C++ Linked List Operation Easy
238 Product of Array Except Self C++ Tricky Medium
239 Sliding Window Maximum C++ Tricky Hard
240 Search a 2D Matrix II C++ Binary Search Medium
241 Different Ways to Add Parentheses C++ DP+Recursion Medium
242 Valid Anagram C++ Data Structure Easy
257 Binary Tree Paths C++ Recursion Easy
258 Add Digits C++ Simulation Easy
260 Single Number III C++ Bit Operations Medium
262 Trips and Users SQL SQL Hard
263 Ugly Number C++ Simulation Easy
264 Ugly Number II C++ Simulation Medium
268 Missing Number C++ Tricky Easy
273 Integer to English Words C++ Simulation Hard
274 H-Index C++ Tricky Medium
275 H-Index II C++ Tricky Medium
278 First Bad Version C++ Binary Search Easy
279 Perfect Squares PY DP Medium
282 Expression Add Operators C++ DFS Hard
283 Move Zeroes PY Simulation Easy
284 Peeking Iterator C++ Simulation Medium
287 Find the Duplicate Number C++ Tricky Medium
289 Game of Life C++ Simulation Medium
292 Nim Game C++ Tricky Easy
301 Remove Invalid Parentheses C++ Brute Force Hard
303 Range Sum Query - Immutable C++ Data Structure Easy
304 Range Sum Query 2D - Immutable C++ Data Structure Medium
306 Additive Number C++ Brute Force Medium
307 Range Sum Query - Mutable C++ Data Structure Medium
309 Best Time to Buy and Sell Stock with Cooldown C++ DP Medium
312 Burst Balloons C++ DP Hard
313 Super Ugly Number C++ DP Medium
315 Count of Smaller Numbers After Self C++ Data Structure Hard
318 Maximum Product of Word Lengths C++ Brute Force Medium
319 Bulb Switcher C++ Trick Medium
321 Create Maximum Number C++ Greedy+DP Hard
324 Wiggle Sort II C++ Greedy+DP Medium
327 Count of Range Sum C++ Data Structure Hard
328 Odd Even Linked List C++ Data Structure Medium
329 Longest Increasing Path in a Matrix C++ DP+DFS Hard
330 Patching Array C++ Tricky Hard
331 Verify Preorder Serialization of a Binary Tree C++ Tricky Medium
332 Reconstruct Itinerary C++ DFS+Tricky Medium
334 Increasing Triplet Subsequence C++ Tricky Medium
335 Self Crossing C++ Tricky Hard
336 Palindrome Pairs C++ Data Structure Hard
341 Flatten Nested List Iterator C++ Data Structure Medium
342 Power of Four C++ Math Easy
343 Integer Break C++ Math Medium
344 Reverse String C++ Data Structure Easy
345 Reverse Vowels of a String C++ Simulation Easy
347 Top K Frequent Elements C++ Data Structure Medium
349 Intersection of Two Arrays C++ Data Structure Easy
350 Intersection of Two Arrays II C++ Data Structure Easy
352 Data Stream as Disjoint Intervals C++ Data Structure Hard
355 Design Twitter C++ Data Structure Medium
357 Count Numbers with Unique Digits C++ Trick Medium
363 Max Sum of Rectangle No Larger Than K C++ Data Structure Hard
365 Water and Jug Problem C++ Trick Medium
367 Valid Perfect Square C++ Trick Easy
368 Largest Divisible Subset C++ DP Medium
371 Sum of Two Integers C++ Trick Medium
372 Super Pow C++ Trick Medium
373 Find K Pairs with Smallest Sums C++ Trick Medium
374 Guess Number Higher or Lower C++ Binary Search Easy
375 Guess Number Higher or Lower II C++ Binary Search Medium
378 Kth Smallest Element in a Sorted Matrix C++ Binary Search Medium
380 Insert Delete GetRandom O(1) C++ Data Structure Medium
381 Insert Delete GetRandom O(1) - Duplicates allowed C++ Data Structure Hard
383 Ransom Note PY String Operations Easy
384 Shuffle an Array C++ Data Structure Medium
385 Mini Parser C++ Recursion Medium
386 Lexicographical Numbers C++ Trick Medium
387 First Unique Character in a String C++ Data Structure Easy
388 Longest Absolute File Path C++ Data Structure Medium
390 Elimination Game C++ Data Structure Medium
391 Perfect Rectangle C++ Bit Operation Hard
392 Is Subsequence PY String Operations Easy
393 UTF-8 Validation C++ Bit Operation Medium
396 Rotate Function C++ Tricky Medium
397 Integer Replacement C++ Tricky Medium
398 Random Pick Index C++ Tricky Medium
400 Nth Digit C++ Tricky Medium
401 Binary Watch C++ Bit Operation Easy
402 Remove K Digits C++ Data Structure Easy
403 Frog Jump C++ DP Hard
404 Sum of Left Leaves C++ Tree Easy
405 Convert a Number to Hexadecimal C++ Tree Easy
406 Queue Reconstruction by Height C++ Tree Medium
407 Trapping Rain Water II C++ BFS Hard
409 Longest Palindrome C++ Brute Force Easy
410 Split Array Largest Sum C++ Binary Search Hard
412 Fizz Buzz C++ Simulation Easy
413 Arithmetic Slices C++ Tricky Medium
414 Third Maximum Number C++ Simulation Easy
416 Partition Equal Subset Sum C++ Data Structure Medium
417 Pacific Atlantic Water Flow C++ Data Structure Medium
419 Battleships in a Board C++ DFS Medium
420 Strong Password Checker C++ Greedy Hard
421 Maximum XOR of Two Numbers in an Array C++ Data Structure Medium
423 Reconstruct Original Digits from English C++ Simulation Medium
424 Longest Repeating Character Replacement C++ Binary Search Medium
427 Construct Quad Tree C++ Recursion Medium
429 N-ary Tree Level Order Traversal C++ DFS Medium
430 Flatten a Multilevel Doubly Linked List C++ Recursion Medium
432 All O`one Data Structure C++ Data Structure Hard
433 Minimum Genetic Mutation C++ DFS Medium
434 Number of Segments in a String PY String Operations Easy
435 Non-overlapping Intervals CPP Greedy Medium
436 Find Right Interval CPP Data Structure Medium
437 Path Sum III CPP DFS Medium
438 Find All Anagrams in a String CPP String Operations Medium
440 K-th Smallest in Lexicographical Order CPP Tricky Hard
441 Arranging Coins CPP Tricky Easy
442 Find All Duplicates in an Array CPP Tricky Medium
443 String Compression CPP String Operations Medium
446 Arithmetic Slices II - Subsequence CPP DP / Tricky Hard
447 Number of Boomerangs CPP Data Structure Medium
448 Find All Numbers Disappeared in an Array CPP Tricky Easy
450 Delete Node in a BST CPP Data Structure Medium
451 Sort Characters By Frequency PY Data Structure Medium
452 Minimum Number of Arrows to Burst Balloons CPP Tricky Medium
453 Minimum Moves to Equal Array Elements PY Tricky Medium
454 4Sum II CPP Data Structure Medium
455 Assign Cookies CPP Greedy Easy
456 132 Pattern CPP Stack Medium
457 Circular Array Loop CPP Simulation Medium
458 Poor Pigs CPP Mathematics HARD
459 Repeated Substring Pattern PY String Operations Easy
460 LFU Cache CPP Mathematics Hard
461 Hamming Distance CPP Bit Operation Easy
462 Minimum Moves to Equal Array Elements II PY Tricky Medium
463 Island Perimeter PY Brute Force Easy
464 Can I Win PY BFS Medium
466 Count The Repetitions CPP Tricky+String Operations Hard
467 Unique Substrings in Wraparound String CPP Tricky Medium
468 Validate IP Address PY String Operations Medium
470 Implement Rand10() Using Rand7() CPP Mathematics Medium
472 Concatenated Words CPP Tricky+DP+String Operations Hard
473 Matchsticks to Square CPP DP+Tricky+DFS Medium
474 Ones and Zeroes CPP DP Medium
475 Heaters CPP Binary Search Medium
477 Total Hamming Distance CPP Bit Operations Medium
478 Generate Random Point in a Circle CPP Mathematics Medium
479 Largest Palindrome Product CPP Brute Force Hard
480 Sliding Window Median CPP Data Structure Hard
481 Magical String CPP Mathematics+String Operations Medium
482 License Key Formatting PY String Operations Easy
483 Smallest Good Base CPP Mathematics Hard
485 Max Consecutive Ones CPP Tricky Easy
486 Predict the Winner CPP DP Medium
488 Zuma Game PY Brute Force Hard
491 Increasing Subsequences PY Brute Force Medium
492 Construct the Rectangle CPP Tricky Easy
493 Reverse Pairs CPP Data Structure Hard
494 Target Sum CPP Brute Force + DP Medium
495 Teemo Attacking CPP Simulation Easy
496 Next Greater Element I CPP Data Structure Easy
497 Random Point in Non-overlapping Rectangles CPP Binary Search Medium
498 Diagonal Traverse PY Tricky Medium
500 Keyboard Row PY Tricky Easy
501 Find Mode in Binary Search Tree PY Data Structure Easy
502 IPO PY Greedy Hard
503 Next Greater Element II PY Data Structure Medium
504 Base 7 PY Tricky Easy
506 Relative Ranks PY Data Structure Easy
507 Perfect Number PY Tricky Easy
508 Most Frequent Subtree Sum PY Data Structure Medium
509 Most Frequent Subtree Sum PY Simulation Easy
513 Find Bottom Left Tree Value PY Data Structure Medium
514 Freedom Trail CPP DP Hard
515 Find Largest Value in Each Tree Row PY Data Structure Medium
516 Longest Palindromic Subsequence PY DP Medium
517 Super Washing Machines PY Greedy Hard
518 Coin Change 2 CPP DP Medium
519 Random Flip Matrix CPP Tricky Medium
520 Detect Capital GO Simulation Easy
521 Longest Uncommon Subsequence I GO Simulation Easy
522 Longest Uncommon Subsequence II GO Greedy Medium
523 Continuous Subarray Sum GO Data Structure Medium
524 Longest Word in Dictionary through Deleting GO String Operations Medium
526 Beautiful Arrangement GO Brute Force Medium
528 Random Pick with Weight C++ Binary Search Medium
529 Minesweeper GO Simulation Medium
530 Minimum Absolute Difference in BST GO Simulation Easy
532 K-diff Pairs in an Array GO Simulation Medium
535 Encode and Decode TinyURL GO String Operation Medium
538 Convert BST to Greater Tree GO DFS Medium
539 Minimum Time Difference GO Tricky Medium
540 Single Element in a Sorted Array CPP Binary Search Medium
541 Reverse String II GO String Operation Easy
542 01 Matrix GO DP Medium
546 Remove Boxes CPP DP Hard
547 Number of Provinces GO Brute Force Medium
551 Student Attendance Record I GO Brute Force Easy
552 Student Attendance Record II C++ Mathematics Hard
553 Optimal Division GO Tricky Medium
554 Brick Wall GO Dynamic Programming Medium
556 Next Greater Element III GO Data Structure Medium
557 Reverse Words in a String III PY String Operations Easy
558 Logical OR of Two Binary Grids Represented as Quad-Trees PY Recursion Medium
559 Maximum Depth of N-ary Tree PY Recursion Easy
560 Subarray Sum Equals K PY Data Structure Medium
561 Array Partition PY Greedy Easy
563 Binary Tree Tilt PY Recursion Easy
564 Find the Closest Palindrome PY Tricky Hard
566 Reshape the Matrix PY Tricky Easy
567 Permutation in String C++ Data Structure Medium
572 Subtree of Another Tree GO Data Structure Easy
575 Distribute Candies GO Simulation Easy
576 Out of Boundary Paths GO Memory Based Search Medium
581 Shortest Unsorted Continuous Subarray GO Tricky Medium
583 Delete Operation for Two Strings GO Dynamic Programming Medium
584 Find Customer Referee SQL Tricky Easy
586 Customer Placing the Largest Number of Orders SQL Tricky Easy
587 Erect the Fence GO Computing Geometry Hard
590 N-ary Tree Postorder Traversal GO DFS Easy
591 Tag Validator PY State Machine Hard
592 Fraction Addition and Subtraction PY Mathematics Medium
594 Longest Harmonious Subsequence GO Mathematics Easy
595 Big Countries SQL Tricky Easy
596 Classes More Than 5 Students SQL Trikcy Easy
599 Minimum Index Sum of Two Lists GO Data Structure Easy
600 Non-negative Integers without Consecutive Ones GO Mathematics Hard
601 Human Traffic of Stadium SQL Tricky Hard
602 Friend Requests II: Who Has the Most Friends SQL Tricky Medium
605 Can Place Flowers GO Greedy Easy
606 Construct String from Binary Tree GO String Operations Easy
607 Sales Person SQL Tricky Easy
608 Tree Node SQL Tricky Easy
610 Triangle Judgement SQL Tricky Easy
611 Valid Triangle Number GO Tricky Medium
617 Merge Two Binary Trees GO Tricky Easy
619 Biggest Single Number SQL Tricky Easy
621 Task Scheduler GO Tricky Medium
622 Design Circular Queue GO Tricky Medium
623 Add One Row to Tree GO Tricky Medium
626 Exchange Seats SQL Tricky Medium
627 Swap Salary SQL Tricky Easy
628 Maximum Product of Three Numbers GO Tricky Easy
630 Course Schedule III GO Data Structure Hard
632 Smallest Range Covering Elements from K Lists GO Tricky + Data Structure Hard
636 Exclusive Time of Functions GO Tricky +Stack Medium
637 Average of Levels in Binary Tree GO Data Structure Easy
638 Shopping Offers PY DFS Medium

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Record my training on LeetCode in my doctoral life

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