Sorting LeetCode Problems: All 392,
With Python Solutions

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

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Easy: 80
Medium: 226
Hard: 86

1 pattern

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.

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

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python

Please analyze this context and help me answer the question or solve the problem.

Technical interview · 45 minsolution.pyShared editor · Python 3Longest substring without repeatsMediumGiven a string s, return the length of the longest contiguous substring in which every character is unique.s = "abcabcbb"
→ 31def length_of_longest_substring(s: str) -> int:2 last_seen = {}3 left = best = 04 for right, ch in enumerate(s):5 if ch in last_seen and last_seen[ch] >= left:

python

def length_of_longest_substring(s: str) -> int:    last_seen = {}                    # char -> index    left = best = 0    for right, ch in enumerate(s):        if ch in last_seen and last_seen[ch] >= left:            left = last_seen[ch] + 1  # jump past it        last_seen[ch] = right        best = max(best, right - left + 1)    return best    last_seen = {}                    # char -> index

Approach

At each index r, the window's left edge is:

left r = max (left r -1, last[s r] + 1)

Time O(n): each character enters and leaves the window once.
Space O(min(n, k)): k is the size of the character set.

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python

Please analyze this context and help me answer the question or solve the problem.

python

def length_of_longest_substring(s: str) -> int:    last_seen = {}                    # char -> index    left = best = 0    for right, ch in enumerate(s):        if ch in last_seen and last_seen[ch] >= left:            left = last_seen[ch] + 1  # jump past it        last_seen[ch] = right        best = max(best, right - left + 1)    return best    last_seen = {}                    # char -> index

Approach

At each index r, the window's left edge is:

left r = max (left r -1, last[s r] + 1)

Time O(n): each character enters and leaves the window once.
Space O(min(n, k)): k is the size of the character set.

Type your message...

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QuitEscHide+QCapture+PCrop+OSubmit+EnterPress to get answerLeft/Right+Up/Down+

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python

Please analyze this context and help me answer the question or solve the problem.

python

def length_of_longest_substring(s: str) -> int:    last_seen = {}                    # char -> index    left = best = 0    for right, ch in enumerate(s):        if ch in last_seen and last_seen[ch] >= left:            left = last_seen[ch] + 1  # jump past it        last_seen[ch] = right        best = max(best, right - left + 1)    return best    last_seen = {}                    # char -> index

Approach

At each index r, the window's left edge is:

left r = max (left r -1, last[s r] + 1)

Time O(n): each character enters and leaves the window once.
Space O(min(n, k)): k is the size of the character set.

Type your message...

GPT-6.1 TerraClear chat

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QuitEscHide+QCapture+PCrop+OSubmit+EnterPress to get answerLeft/Right+Up/Down+

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)

Easy problems
No.	Problem	Topics
0088	Merge Sorted Array	Array, Two Pointers, Sorting
0169	Majority Element	Array, Hash Table, Divide and Conquer +2
0217	Contains Duplicate	Array, Hash Table, Sorting
0242	Valid Anagram	Hash Table, String, Sorting
0268	Missing Number	Bit Manipulation, Array, Hash Table +3
0349	Intersection of Two Arrays	Array, Hash Table, Two Pointers +2
0350	Intersection of Two Arrays II	Array, Hash Table, Two Pointers +2
0389	Find the Difference	Bit Manipulation, Hash Table, String +1
0414	Third Maximum Number	Array, Sorting
0455	Assign Cookies	Greedy, Array, Two Pointers +1
0506	Relative Ranks	Array, Sorting, Heap (Priority Queue)
0561	Array Partition	Greedy, Array, Counting Sort +1
0594	Longest Harmonious Subsequence	Array, Hash Table, Counting +2
0628	Maximum Product of Three Numbers	Array, Math, Sorting
0645	Set Mismatch	Bit Manipulation, Array, Hash Table +1
0747	Largest Number At Least Twice of Others	Array, Sorting
0888	Fair Candy Swap	Array, Hash Table, Binary Search +1
0905	Sort Array By Parity	Array, Two Pointers, Sorting
0922	Sort Array By Parity II	Array, Two Pointers, Sorting
0976	Largest Perimeter Triangle	Greedy, Array, Math +1
0977	Squares of a Sorted Array	Array, Two Pointers, Sorting
1005	Maximize Sum Of Array After K Negations	Greedy, Array, Sorting
1030	Matrix Cells in Distance Order	Geometry, Array, Math +2
1051	Height Checker	Array, Counting Sort, Sorting
1122	Relative Sort Array	Array, Hash Table, Counting Sort +1
1200	Minimum Absolute Difference	Array, Sorting
1331	Rank Transform of an Array	Array, Hash Table, Sorting
1337	The K Weakest Rows in a Matrix	Array, Binary Search, Matrix +2
1346	Check If N and Its Double Exist	Array, Hash Table, Two Pointers +2
1356	Sort Integers by The Number of 1 Bits	Bit Manipulation, Array, Counting +1
1365	How Many Numbers Are Smaller Than the Current Number	Array, Hash Table, Counting Sort +1
1385	Find the Distance Value Between Two Arrays	Array, Two Pointers, Binary Search +1
1403	Minimum Subsequence in Non-Increasing Order	Greedy, Array, Sorting
1460	Make Two Arrays Equal by Reversing Subarrays	Array, Hash Table, Sorting
1464	Maximum Product of Two Elements in an Array	Array, Sorting, Heap (Priority Queue)
1491	Average Salary Excluding the Minimum and Maximum Salary	Array, Sorting
1502	Can Make Arithmetic Progression From Sequence	Array, Sorting
1608	Special Array With X Elements Greater Than or Equal X	Array, Binary Search, Sorting
1619	Mean of Array After Removing Some Elements	Array, Sorting
1636	Sort Array by Increasing Frequency	Array, Hash Table, Sorting
1637	Widest Vertical Area Between Two Points Containing No Points	Array, Sorting
1710	Maximum Units on a Truck	Greedy, Array, Sorting
1859	Sorting the Sentence	String, Sorting

Medium (118)

Medium problems
No.	Problem	Topics
0015	3Sum	Array, Two Pointers, Sorting
0016	3Sum Closest	Array, Two Pointers, Sorting
0018	4Sum	Array, Two Pointers, Sorting
0047	Permutations II	Array, Backtracking, Sorting
0049	Group Anagrams	Array, Hash Table, String +1
0056	Merge Intervals	Array, Sorting
0075	Sort Colors	Array, Two Pointers, Sorting
0147	Insertion Sort List	Linked List, Sorting
0148	Sort List	Linked List, Two Pointers, Divide and Conquer +2
0164	Maximum Gap	Array, Bucket Sort, Radix Sort +1
0179	Largest Number	Greedy, Array, String +1
0215	Kth Largest Element in an Array	Array, Divide and Conquer, Quickselect +2
0229	Majority Element II	Array, Hash Table, Counting +1
0274	H-Index	Array, Counting Sort, Sorting
0324	Wiggle Sort II	Greedy, Array, Divide and Conquer +2
0347	Top K Frequent Elements	Array, Hash Table, Divide and Conquer +5
0368	Largest Divisible Subset	Array, Math, Dynamic Programming +1
0378	Kth Smallest Element in a Sorted Matrix	Array, Binary Search, Matrix +2
0406	Queue Reconstruction by Height	Binary Indexed Tree, Segment Tree, Array +1
0435	Non-overlapping Intervals	Greedy, Array, Dynamic Programming +1
0436	Find Right Interval	Array, Binary Search, Sorting
0442	Find All Duplicates in an Array	Array, Hash Table, Sorting
0451	Sort Characters By Frequency	Hash Table, String, Bucket Sort +3
0452	Minimum Number of Arrows to Burst Balloons	Greedy, Array, Sorting
0462	Minimum Moves to Equal Array Elements II	Array, Math, Sorting
0475	Heaters	Array, Two Pointers, Binary Search +1
0522	Longest Uncommon Subsequence II	Array, Hash Table, Two Pointers +2
0524	Longest Word in Dictionary through Deleting	Array, Two Pointers, String +1
0532	K-diff Pairs in an Array	Array, Hash Table, Two Pointers +2
0539	Minimum Time Difference	Array, Math, String +1
0581	Shortest Unsorted Continuous Subarray	Stack, Greedy, Array +3
0611	Valid Triangle Number	Greedy, Array, Two Pointers +2
0621	Task Scheduler	Greedy, Array, Hash Table +3
0646	Maximum Length of Pair Chain	Greedy, Array, Dynamic Programming +1
0658	Find K Closest Elements	Array, Two Pointers, Binary Search +3
0692	Top K Frequent Words	Trie, Array, Hash Table +5
0720	Longest Word in Dictionary	Trie, Array, Hash Table +2
0721	Accounts Merge	Depth-First Search, Breadth-First Search, Union Find +4
0767	Reorganize String	Greedy, Hash Table, String +3
0769	Max Chunks To Make Sorted	Stack, Greedy, Array +2
0786	K-th Smallest Prime Fraction	Array, Two Pointers, Binary Search +2
0791	Custom Sort String	Hash Table, String, Sorting
0792	Number of Matching Subsequences	Trie, Array, Hash Table +4
0823	Binary Trees With Factors	Array, Hash Table, Dynamic Programming +1
0825	Friends Of Appropriate Ages	Array, Two Pointers, Binary Search +1
0826	Most Profit Assigning Work	Greedy, Array, Two Pointers +2
0833	Find And Replace in String	Array, Hash Table, String +1
0846	Hand of Straights	Greedy, Array, Hash Table +1
0853	Car Fleet	Stack, Array, Sorting +1
0869	Reordered Power of 2	Hash Table, Math, Counting +2
0870	Advantage Shuffle	Greedy, Array, Two Pointers +1
0881	Boats to Save People	Greedy, Array, Two Pointers +1
0893	Groups of Special-Equivalent Strings	Array, Hash Table, String +1
0910	Smallest Range II	Greedy, Array, Math +1
0912	Sort an Array	Array, Divide and Conquer, Bucket Sort +5
0923	3Sum With Multiplicity	Array, Hash Table, Two Pointers +2
0937	Reorder Data in Log Files	Array, String, Sorting
0939	Minimum Area Rectangle	Geometry, Array, Hash Table +2
0945	Minimum Increment to Make Array Unique	Greedy, Array, Counting +1
0948	Bag of Tokens	Greedy, Array, Two Pointers +1
0950	Reveal Cards In Increasing Order	Queue, Array, Sorting +1
0954	Array of Doubled Pairs	Greedy, Array, Hash Table +1
0969	Pancake Sorting	Greedy, Array, Two Pointers +1
0973	K Closest Points to Origin	Geometry, Array, Math +4
1029	Two City Scheduling	Greedy, Array, Sorting
1040	Moving Stones Until Consecutive II	Array, Math, Sorting +1
1048	Longest String Chain	Array, Hash Table, Two Pointers +3
1054	Distant Barcodes	Greedy, Array, Hash Table +3
1090	Largest Values From Labels	Greedy, Array, Hash Table +2
1094	Car Pooling	Array, Prefix Sum, Sorting +2
1169	Invalid Transactions	Array, Hash Table, String +1
1170	Compare Strings by Frequency of the Smallest Character	Array, Hash Table, String +2
1202	Smallest String With Swaps	Depth-First Search, Breadth-First Search, Union Find +4
1262	Greatest Sum Divisible by Three	Greedy, Array, Dynamic Programming +1
1268	Search Suggestions System	Trie, Array, String +3
1288	Remove Covered Intervals	Array, Sorting
1296	Divide Array in Sets of K Consecutive Numbers	Greedy, Array, Hash Table +1
1300	Sum of Mutated Array Closest to Target	Array, Binary Search, Sorting
1305	All Elements in Two Binary Search Trees	Tree, Depth-First Search, Binary Search Tree +2
1311	Get Watched Videos by Your Friends	Breadth-First Search, Graph, Array +2
1329	Sort the Matrix Diagonally	Array, Matrix, Sorting
1333	Filter Restaurants by Vegan-Friendly, Price and Distance	Array, Sorting
1338	Reduce Array Size to The Half	Greedy, Array, Hash Table +2
1348	Tweet Counts Per Frequency	Design, Hash Table, String +3
1353	Maximum Number of Events That Can Be Attended	Greedy, Array, Sorting +1
1366	Rank Teams by Votes	Array, Hash Table, String +2
1387	Sort Integers by The Power Value	Memoization, Dynamic Programming, Sorting
1418	Display Table of Food Orders in a Restaurant	Array, Hash Table, String +2
1424	Diagonal Traverse II	Array, Sorting, Heap (Priority Queue)
1433	Check If a String Can Break Another String	Greedy, String, Sorting
1451	Rearrange Words in a Sentence	String, Sorting
1465	Maximum Area of a Piece of Cake After Horizontal and Vertical Cuts	Greedy, Array, Sorting
1471	The k Strongest Values in an Array	Array, Two Pointers, Sorting
1481	Least Number of Unique Integers after K Removals	Greedy, Array, Hash Table +2
1498	Number of Subsequences That Satisfy the Given Sum Condition	Array, Two Pointers, Binary Search +1
1508	Range Sum of Sorted Subarray Sums	Array, Two Pointers, Binary Search +2
1509	Minimum Difference Between Largest and Smallest Value in Three Moves	Greedy, Array, Sorting
1552	Magnetic Force Between Two Balls	Array, Binary Search, Sorting
1561	Maximum Number of Coins You Can Get	Greedy, Array, Math +2
1589	Maximum Sum Obtained of Any Permutation	Greedy, Array, Prefix Sum +1
1604	Alert Using Same Key-Card Three or More Times in a One Hour Period	Array, Hash Table, String +1
1626	Best Team With No Conflicts	Array, Dynamic Programming, Sorting
1630	Arithmetic Subarrays	Array, Hash Table, Sorting
1647	Minimum Deletions to Make Character Frequencies Unique	Greedy, Hash Table, String +1
1648	Sell Diminishing-Valued Colored Balls	Greedy, Array, Math +3
1657	Determine if Two Strings Are Close	Hash Table, String, Counting +1
1679	Max Number of K-Sum Pairs	Array, Hash Table, Two Pointers +1
1686	Stone Game VI	Greedy, Array, Math +3
1727	Largest Submatrix With Rearrangements	Greedy, Array, Matrix +1
1738	Find Kth Largest XOR Coordinate Value	Bit Manipulation, Array, Divide and Conquer +5
1798	Maximum Number of Consecutive Values You Can Make	Greedy, Array, Sorting
1818	Minimum Absolute Sum Difference	Array, Binary Search, Ordered Set +1
1833	Maximum Ice Cream Bars	Greedy, Array, Counting Sort +1
1834	Single-Threaded CPU	Array, Sorting, Heap (Priority Queue)
1838	Frequency of the Most Frequent Element	Greedy, Array, Binary Search +3
1846	Maximum Element After Decreasing and Rearranging	Greedy, Array, Sorting
1877	Minimize Maximum Pair Sum in Array	Greedy, Array, Two Pointers +1
1878	Get Biggest Three Rhombus Sums in a Grid	Array, Math, Matrix +3

Hard (39)

Hard problems
No.	Problem	Topics
0218	The Skyline Problem	Binary Indexed Tree, Segment Tree, Array +5
0220	Contains Duplicate III	Array, Bucket Sort, Ordered Set +2
0295	Find Median from Data Stream	Design, Two Pointers, Data Stream +2
0354	Russian Doll Envelopes	Array, Binary Search, Dynamic Programming +1
0472	Concatenated Words	Depth-First Search, Trie, Array +3
0502	IPO	Greedy, Array, Sorting +1
0630	Course Schedule III	Greedy, Array, Sorting +1
0632	Smallest Range Covering Elements from K Lists	Greedy, Array, Hash Table +3
0710	Random Pick with Blacklist	Array, Hash Table, Math +3
0719	Find K-th Smallest Pair Distance	Array, Two Pointers, Binary Search +1
0757	Set Intersection Size At Least Two	Greedy, Array, Sorting
0768	Max Chunks To Make Sorted II	Stack, Greedy, Array +2
0857	Minimum Cost to Hire K Workers	Greedy, Array, Sorting +1
0891	Sum of Subsequence Widths	Array, Math, Sorting
0899	Orderly Queue	Math, String, Sorting
0975	Odd Even Jump	Stack, Array, Dynamic Programming +3
0987	Vertical Order Traversal of a Binary Tree	Tree, Depth-First Search, Breadth-First Search +3
1096	Brace Expansion II	Stack, Breadth-First Search, Hash Table +3
1187	Make Array Strictly Increasing	Array, Binary Search, Dynamic Programming +1
1235	Maximum Profit in Job Scheduling	Array, Binary Search, Dynamic Programming +1
1340	Jump Game V	Array, Dynamic Programming, Sorting
1363	Largest Multiple of Three	Greedy, Array, Math +2
1383	Maximum Performance of a Team	Greedy, Array, Sorting +1
1402	Reducing Dishes	Greedy, Array, Dynamic Programming +1
1478	Allocate Mailboxes	Array, Math, Dynamic Programming +1
1489	Find Critical and Pseudo-Critical Edges in Minimum Spanning Tree	Union Find, Graph, Minimum Spanning Tree +2
1547	Minimum Cost to Cut a Stick	Array, Dynamic Programming, Sorting
1585	Check If String Is Transformable With Substring Sort Operations	Greedy, String, Sorting
1610	Maximum Number of Visible Points	Geometry, Array, Math +2
1632	Rank Transform of a Matrix	Union Find, Graph, Topological Sort +3
1665	Minimum Initial Energy to Finish Tasks	Greedy, Array, Sorting
1691	Maximum Height by Stacking Cuboids	Array, Dynamic Programming, Sorting
1697	Checking Existence of Edge Length Limited Paths	Union Find, Graph, Array +2
1751	Maximum Number of Events That Can Be Attended II	Array, Binary Search, Dynamic Programming +1
1755	Closest Subsequence Sum	Bit Manipulation, Array, Two Pointers +3
1782	Count Pairs Of Nodes	Graph, Array, Hash Table +4
1840	Maximum Building Height	Array, Math, Sorting
1847	Closest Room	Array, Binary Search, Ordered Set +1
1851	Minimum Interval to Include Each Query	Array, Binary Search, Sorting +2

How Sorting problems are solved

When the Sorting problem arrives live.

Approach

Approach

Approach

Sorting problems by difficulty

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Medium (118)118

Hard (39)39

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