Sorting LeetCode Problems: All 392, With Python Solutions

Every problem in this library that LeetCode tags Sorting — 392 in total, 339 of them with a complete Python solution, a worked example and the time and space complexity of the approach.

392 problems
80 Easy
226 Medium
86 Hard

How Sorting problems are solved

A tag names the subject, not the method. These pattern hubs cover the techniques that actually solve Sorting problems — each one explains the approach, gives a Python template and states its complexity.

Sorting — Spend O(n log n) once to buy an ordering that makes the rest of the problem trivial.

Sorting problems by difficulty

Showing the first 200 of 392 problems. Problems with a complete Python solution are listed first, then by ascending problem number.

Easy (43)

#	Problem	Difficulty	Topics
88	Merge Sorted Array	Easy	Array, Two Pointers, Sorting
169	Majority Element	Easy	Array, Hash Table, Divide and Conquer +2
217	Contains Duplicate	Easy	Array, Hash Table, Sorting
242	Valid Anagram	Easy	Hash Table, String, Sorting
268	Missing Number	Easy	Bit Manipulation, Array, Hash Table +3
349	Intersection of Two Arrays	Easy	Array, Hash Table, Two Pointers +2
350	Intersection of Two Arrays II	Easy	Array, Hash Table, Two Pointers +2
389	Find the Difference	Easy	Bit Manipulation, Hash Table, String +1
414	Third Maximum Number	Easy	Array, Sorting
455	Assign Cookies	Easy	Greedy, Array, Two Pointers +1
506	Relative Ranks	Easy	Array, Sorting, Heap (Priority Queue)
561	Array Partition	Easy	Greedy, Array, Counting Sort +1
594	Longest Harmonious Subsequence	Easy	Array, Hash Table, Counting +2
628	Maximum Product of Three Numbers	Easy	Array, Math, Sorting
645	Set Mismatch	Easy	Bit Manipulation, Array, Hash Table +1
747	Largest Number At Least Twice of Others	Easy	Array, Sorting
888	Fair Candy Swap	Easy	Array, Hash Table, Binary Search +1
905	Sort Array By Parity	Easy	Array, Two Pointers, Sorting
922	Sort Array By Parity II	Easy	Array, Two Pointers, Sorting
976	Largest Perimeter Triangle	Easy	Greedy, Array, Math +1
977	Squares of a Sorted Array	Easy	Array, Two Pointers, Sorting
1005	Maximize Sum Of Array After K Negations	Easy	Greedy, Array, Sorting
1030	Matrix Cells in Distance Order	Easy	Geometry, Array, Math +2
1051	Height Checker	Easy	Array, Counting Sort, Sorting
1122	Relative Sort Array	Easy	Array, Hash Table, Counting Sort +1
1200	Minimum Absolute Difference	Easy	Array, Sorting
1331	Rank Transform of an Array	Easy	Array, Hash Table, Sorting
1337	The K Weakest Rows in a Matrix	Easy	Array, Binary Search, Matrix +2
1346	Check If N and Its Double Exist	Easy	Array, Hash Table, Two Pointers +2
1356	Sort Integers by The Number of 1 Bits	Easy	Bit Manipulation, Array, Counting +1
1365	How Many Numbers Are Smaller Than the Current Number	Easy	Array, Hash Table, Counting Sort +1
1385	Find the Distance Value Between Two Arrays	Easy	Array, Two Pointers, Binary Search +1
1403	Minimum Subsequence in Non-Increasing Order	Easy	Greedy, Array, Sorting
1460	Make Two Arrays Equal by Reversing Subarrays	Easy	Array, Hash Table, Sorting
1464	Maximum Product of Two Elements in an Array	Easy	Array, Sorting, Heap (Priority Queue)
1491	Average Salary Excluding the Minimum and Maximum Salary	Easy	Array, Sorting
1502	Can Make Arithmetic Progression From Sequence	Easy	Array, Sorting
1608	Special Array With X Elements Greater Than or Equal X	Easy	Array, Binary Search, Sorting
1619	Mean of Array After Removing Some Elements	Easy	Array, Sorting
1636	Sort Array by Increasing Frequency	Easy	Array, Hash Table, Sorting
1637	Widest Vertical Area Between Two Points Containing No Points	Easy	Array, Sorting
1710	Maximum Units on a Truck	Easy	Greedy, Array, Sorting
1859	Sorting the Sentence	Easy	String, Sorting

Medium (118)

#	Problem	Difficulty	Topics
15	3Sum	Medium	Array, Two Pointers, Sorting
16	3Sum Closest	Medium	Array, Two Pointers, Sorting
18	4Sum	Medium	Array, Two Pointers, Sorting
47	Permutations II	Medium	Array, Backtracking, Sorting
49	Group Anagrams	Medium	Array, Hash Table, String +1
56	Merge Intervals	Medium	Array, Sorting
75	Sort Colors	Medium	Array, Two Pointers, Sorting
147	Insertion Sort List	Medium	Linked List, Sorting
148	Sort List	Medium	Linked List, Two Pointers, Divide and Conquer +2
164	Maximum Gap	Medium	Array, Bucket Sort, Radix Sort +1
179	Largest Number	Medium	Greedy, Array, String +1
215	Kth Largest Element in an Array	Medium	Array, Divide and Conquer, Quickselect +2
229	Majority Element II	Medium	Array, Hash Table, Counting +1
274	H-Index	Medium	Array, Counting Sort, Sorting
324	Wiggle Sort II	Medium	Greedy, Array, Divide and Conquer +2
347	Top K Frequent Elements	Medium	Array, Hash Table, Divide and Conquer +5
368	Largest Divisible Subset	Medium	Array, Math, Dynamic Programming +1
378	Kth Smallest Element in a Sorted Matrix	Medium	Array, Binary Search, Matrix +2
406	Queue Reconstruction by Height	Medium	Binary Indexed Tree, Segment Tree, Array +1
435	Non-overlapping Intervals	Medium	Greedy, Array, Dynamic Programming +1
436	Find Right Interval	Medium	Array, Binary Search, Sorting
442	Find All Duplicates in an Array	Medium	Array, Hash Table, Sorting
451	Sort Characters By Frequency	Medium	Hash Table, String, Bucket Sort +3
452	Minimum Number of Arrows to Burst Balloons	Medium	Greedy, Array, Sorting
462	Minimum Moves to Equal Array Elements II	Medium	Array, Math, Sorting
475	Heaters	Medium	Array, Two Pointers, Binary Search +1
522	Longest Uncommon Subsequence II	Medium	Array, Hash Table, Two Pointers +2
524	Longest Word in Dictionary through Deleting	Medium	Array, Two Pointers, String +1
532	K-diff Pairs in an Array	Medium	Array, Hash Table, Two Pointers +2
539	Minimum Time Difference	Medium	Array, Math, String +1
581	Shortest Unsorted Continuous Subarray	Medium	Stack, Greedy, Array +3
611	Valid Triangle Number	Medium	Greedy, Array, Two Pointers +2
621	Task Scheduler	Medium	Greedy, Array, Hash Table +3
646	Maximum Length of Pair Chain	Medium	Greedy, Array, Dynamic Programming +1
658	Find K Closest Elements	Medium	Array, Two Pointers, Binary Search +3
692	Top K Frequent Words	Medium	Trie, Array, Hash Table +5
720	Longest Word in Dictionary	Medium	Trie, Array, Hash Table +2
721	Accounts Merge	Medium	Depth-First Search, Breadth-First Search, Union Find +4
767	Reorganize String	Medium	Greedy, Hash Table, String +3
769	Max Chunks To Make Sorted	Medium	Stack, Greedy, Array +2
786	K-th Smallest Prime Fraction	Medium	Array, Two Pointers, Binary Search +2
791	Custom Sort String	Medium	Hash Table, String, Sorting
792	Number of Matching Subsequences	Medium	Trie, Array, Hash Table +4
823	Binary Trees With Factors	Medium	Array, Hash Table, Dynamic Programming +1
825	Friends Of Appropriate Ages	Medium	Array, Two Pointers, Binary Search +1
826	Most Profit Assigning Work	Medium	Greedy, Array, Two Pointers +2
833	Find And Replace in String	Medium	Array, Hash Table, String +1
846	Hand of Straights	Medium	Greedy, Array, Hash Table +1
853	Car Fleet	Medium	Stack, Array, Sorting +1
869	Reordered Power of 2	Medium	Hash Table, Math, Counting +2
870	Advantage Shuffle	Medium	Greedy, Array, Two Pointers +1
881	Boats to Save People	Medium	Greedy, Array, Two Pointers +1
893	Groups of Special-Equivalent Strings	Medium	Array, Hash Table, String +1
910	Smallest Range II	Medium	Greedy, Array, Math +1
912	Sort an Array	Medium	Array, Divide and Conquer, Bucket Sort +5
923	3Sum With Multiplicity	Medium	Array, Hash Table, Two Pointers +2
937	Reorder Data in Log Files	Medium	Array, String, Sorting
939	Minimum Area Rectangle	Medium	Geometry, Array, Hash Table +2
945	Minimum Increment to Make Array Unique	Medium	Greedy, Array, Counting +1
948	Bag of Tokens	Medium	Greedy, Array, Two Pointers +1
950	Reveal Cards In Increasing Order	Medium	Queue, Array, Sorting +1
954	Array of Doubled Pairs	Medium	Greedy, Array, Hash Table +1
969	Pancake Sorting	Medium	Greedy, Array, Two Pointers +1
973	K Closest Points to Origin	Medium	Geometry, Array, Math +4
1029	Two City Scheduling	Medium	Greedy, Array, Sorting
1040	Moving Stones Until Consecutive II	Medium	Array, Math, Sorting +1
1048	Longest String Chain	Medium	Array, Hash Table, Two Pointers +3
1054	Distant Barcodes	Medium	Greedy, Array, Hash Table +3
1090	Largest Values From Labels	Medium	Greedy, Array, Hash Table +2
1094	Car Pooling	Medium	Array, Prefix Sum, Sorting +2
1169	Invalid Transactions	Medium	Array, Hash Table, String +1
1170	Compare Strings by Frequency of the Smallest Character	Medium	Array, Hash Table, String +2
1202	Smallest String With Swaps	Medium	Depth-First Search, Breadth-First Search, Union Find +4
1262	Greatest Sum Divisible by Three	Medium	Greedy, Array, Dynamic Programming +1
1268	Search Suggestions System	Medium	Trie, Array, String +3
1288	Remove Covered Intervals	Medium	Array, Sorting
1296	Divide Array in Sets of K Consecutive Numbers	Medium	Greedy, Array, Hash Table +1
1300	Sum of Mutated Array Closest to Target	Medium	Array, Binary Search, Sorting
1305	All Elements in Two Binary Search Trees	Medium	Tree, Depth-First Search, Binary Search Tree +2
1311	Get Watched Videos by Your Friends	Medium	Breadth-First Search, Graph, Array +2
1329	Sort the Matrix Diagonally	Medium	Array, Matrix, Sorting
1333	Filter Restaurants by Vegan-Friendly, Price and Distance	Medium	Array, Sorting
1338	Reduce Array Size to The Half	Medium	Greedy, Array, Hash Table +2
1348	Tweet Counts Per Frequency	Medium	Design, Hash Table, String +3
1353	Maximum Number of Events That Can Be Attended	Medium	Greedy, Array, Sorting +1
1366	Rank Teams by Votes	Medium	Array, Hash Table, String +2
1387	Sort Integers by The Power Value	Medium	Memoization, Dynamic Programming, Sorting
1418	Display Table of Food Orders in a Restaurant	Medium	Array, Hash Table, String +2
1424	Diagonal Traverse II	Medium	Array, Sorting, Heap (Priority Queue)
1433	Check If a String Can Break Another String	Medium	Greedy, String, Sorting
1451	Rearrange Words in a Sentence	Medium	String, Sorting
1465	Maximum Area of a Piece of Cake After Horizontal and Vertical Cuts	Medium	Greedy, Array, Sorting
1471	The k Strongest Values in an Array	Medium	Array, Two Pointers, Sorting
1481	Least Number of Unique Integers after K Removals	Medium	Greedy, Array, Hash Table +2
1498	Number of Subsequences That Satisfy the Given Sum Condition	Medium	Array, Two Pointers, Binary Search +1
1508	Range Sum of Sorted Subarray Sums	Medium	Array, Two Pointers, Binary Search +2
1509	Minimum Difference Between Largest and Smallest Value in Three Moves	Medium	Greedy, Array, Sorting
1552	Magnetic Force Between Two Balls	Medium	Array, Binary Search, Sorting
1561	Maximum Number of Coins You Can Get	Medium	Greedy, Array, Math +2
1589	Maximum Sum Obtained of Any Permutation	Medium	Greedy, Array, Prefix Sum +1
1604	Alert Using Same Key-Card Three or More Times in a One Hour Period	Medium	Array, Hash Table, String +1
1626	Best Team With No Conflicts	Medium	Array, Dynamic Programming, Sorting
1630	Arithmetic Subarrays	Medium	Array, Hash Table, Sorting
1647	Minimum Deletions to Make Character Frequencies Unique	Medium	Greedy, Hash Table, String +1
1648	Sell Diminishing-Valued Colored Balls	Medium	Greedy, Array, Math +3
1657	Determine if Two Strings Are Close	Medium	Hash Table, String, Counting +1
1679	Max Number of K-Sum Pairs	Medium	Array, Hash Table, Two Pointers +1
1686	Stone Game VI	Medium	Greedy, Array, Math +3
1727	Largest Submatrix With Rearrangements	Medium	Greedy, Array, Matrix +1
1738	Find Kth Largest XOR Coordinate Value	Medium	Bit Manipulation, Array, Divide and Conquer +5
1798	Maximum Number of Consecutive Values You Can Make	Medium	Greedy, Array, Sorting
1818	Minimum Absolute Sum Difference	Medium	Array, Binary Search, Ordered Set +1
1833	Maximum Ice Cream Bars	Medium	Greedy, Array, Counting Sort +1
1834	Single-Threaded CPU	Medium	Array, Sorting, Heap (Priority Queue)
1838	Frequency of the Most Frequent Element	Medium	Greedy, Array, Binary Search +3
1846	Maximum Element After Decreasing and Rearranging	Medium	Greedy, Array, Sorting
1877	Minimize Maximum Pair Sum in Array	Medium	Greedy, Array, Two Pointers +1
1878	Get Biggest Three Rhombus Sums in a Grid	Medium	Array, Math, Matrix +3

Hard (39)

#	Problem	Difficulty	Topics
218	The Skyline Problem	Hard	Binary Indexed Tree, Segment Tree, Array +5
220	Contains Duplicate III	Hard	Array, Bucket Sort, Ordered Set +2
295	Find Median from Data Stream	Hard	Design, Two Pointers, Data Stream +2
354	Russian Doll Envelopes	Hard	Array, Binary Search, Dynamic Programming +1
472	Concatenated Words	Hard	Depth-First Search, Trie, Array +3
502	IPO	Hard	Greedy, Array, Sorting +1
630	Course Schedule III	Hard	Greedy, Array, Sorting +1
632	Smallest Range Covering Elements from K Lists	Hard	Greedy, Array, Hash Table +3
710	Random Pick with Blacklist	Hard	Array, Hash Table, Math +3
719	Find K-th Smallest Pair Distance	Hard	Array, Two Pointers, Binary Search +1
757	Set Intersection Size At Least Two	Hard	Greedy, Array, Sorting
768	Max Chunks To Make Sorted II	Hard	Stack, Greedy, Array +2
857	Minimum Cost to Hire K Workers	Hard	Greedy, Array, Sorting +1
891	Sum of Subsequence Widths	Hard	Array, Math, Sorting
899	Orderly Queue	Hard	Math, String, Sorting
975	Odd Even Jump	Hard	Stack, Array, Dynamic Programming +3
987	Vertical Order Traversal of a Binary Tree	Hard	Tree, Depth-First Search, Breadth-First Search +3
1096	Brace Expansion II	Hard	Stack, Breadth-First Search, Hash Table +3
1187	Make Array Strictly Increasing	Hard	Array, Binary Search, Dynamic Programming +1
1235	Maximum Profit in Job Scheduling	Hard	Array, Binary Search, Dynamic Programming +1
1340	Jump Game V	Hard	Array, Dynamic Programming, Sorting
1363	Largest Multiple of Three	Hard	Greedy, Array, Math +2
1383	Maximum Performance of a Team	Hard	Greedy, Array, Sorting +1
1402	Reducing Dishes	Hard	Greedy, Array, Dynamic Programming +1
1478	Allocate Mailboxes	Hard	Array, Math, Dynamic Programming +1
1489	Find Critical and Pseudo-Critical Edges in Minimum Spanning Tree	Hard	Union Find, Graph, Minimum Spanning Tree +2
1547	Minimum Cost to Cut a Stick	Hard	Array, Dynamic Programming, Sorting
1585	Check If String Is Transformable With Substring Sort Operations	Hard	Greedy, String, Sorting
1610	Maximum Number of Visible Points	Hard	Geometry, Array, Math +2
1632	Rank Transform of a Matrix	Hard	Union Find, Graph, Topological Sort +3
1665	Minimum Initial Energy to Finish Tasks	Hard	Greedy, Array, Sorting
1691	Maximum Height by Stacking Cuboids	Hard	Array, Dynamic Programming, Sorting
1697	Checking Existence of Edge Length Limited Paths	Hard	Union Find, Graph, Array +2
1751	Maximum Number of Events That Can Be Attended II	Hard	Array, Binary Search, Dynamic Programming +1
1755	Closest Subsequence Sum	Hard	Bit Manipulation, Array, Two Pointers +3
1782	Count Pairs Of Nodes	Hard	Graph, Array, Hash Table +4
1840	Maximum Building Height	Hard	Array, Math, Sorting
1847	Closest Room	Hard	Array, Binary Search, Ordered Set +1
1851	Minimum Interval to Include Each Query	Hard	Array, Binary Search, Sorting +2

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