The NeetCode 150 LeetCode List

An expansion of the Blind 75 into eighteen topic groups, from arrays and hashing through advanced graphs and two-dimensional dynamic programming.

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Easy: 28
Medium: 101
Hard: 21
Patterns: 22

Every entry, grouped by pattern

Each group is the pattern that most specifically solves those problems, so the list can be worked through a technique at a time instead of a problem at a time. Groups appear in the order the list itself introduces them.

Sorting (5)

Sorting
No.	Problem	Difficulty	Topics
0217	Contains Duplicate	Easy	Array, Hash Table, Sorting
0242	Valid Anagram	Easy	Hash Table, String, Sorting
0049	Group Anagrams	Medium	Array, Hash Table, String +1
0056	Merge Intervals	Medium	Array, Sorting
0252	Meeting RoomsPremium	Easy	Array, Sorting

Hash Map (2)

Hash Map
No.	Problem	Difficulty	Topics
0001	Two Sum	Easy	Array, Hash Table
2013	Detect Squares	Medium	Design, Array, Hash Table +1

Heap / Priority Queue (10)

Heap / Priority Queue
No.	Problem	Difficulty	Topics
0347	Top K Frequent Elements	Medium	Array, Hash Table, Divide and Conquer +5
0703	Kth Largest Element in a Stream	Easy	Tree, Design, Binary Search Tree +3
1046	Last Stone Weight	Easy	Array, Heap (Priority Queue)
0973	K Closest Points to Origin	Medium	Geometry, Array, Math +4
0215	Kth Largest Element in an Array	Medium	Array, Divide and Conquer, Quickselect +2
0621	Task Scheduler	Medium	Greedy, Array, Hash Table +3
0295	Find Median from Data Stream	Hard	Design, Two Pointers, Data Stream +2
0743	Network Delay Time	Medium	Depth-First Search, Breadth-First Search, Graph +2
0787	Cheapest Flights Within K Stops	Medium	Depth-First Search, Breadth-First Search, Graph +3
1851	Minimum Interval to Include Each Query	Hard	Array, Binary Search, Sorting +2

Other (2)

Other
No.	Problem	Difficulty	Topics
0271	Encode and Decode StringsPremium	Medium	Design, Array, String
0057	Insert Interval	Medium	Array

Prefix Sum (2)

Prefix Sum
No.	Problem	Difficulty	Topics
0238	Product of Array Except Self	Medium	Array, Prefix Sum
0253	Meeting Rooms IIPremium	Medium	Greedy, Array, Two Pointers +3

Matrix and Grid (8)

Matrix and Grid
No.	Problem	Difficulty	Topics
0036	Valid Sudoku	Medium	Array, Hash Table, Matrix
0074	Search a 2D Matrix	Medium	Array, Binary Search, Matrix
0417	Pacific Atlantic Water Flow	Medium	Depth-First Search, Breadth-First Search, Array +1
0994	Rotting Oranges	Medium	Breadth-First Search, Array, Matrix
0286	Walls and GatesPremium	Medium	Breadth-First Search, Array, Matrix
0048	Rotate Image	Medium	Array, Math, Matrix
0054	Spiral Matrix	Medium	Array, Matrix, Simulation
0073	Set Matrix Zeroes	Medium	Array, Hash Table, Matrix

Union-Find (9)

Union-Find
No.	Problem	Difficulty	Topics
0128	Longest Consecutive Sequence	Medium	Union Find, Array, Hash Table
0200	Number of Islands	Medium	Depth-First Search, Breadth-First Search, Union Find +2
0695	Max Area of Island	Medium	Depth-First Search, Breadth-First Search, Union Find +2
0130	Surrounded Regions	Medium	Depth-First Search, Breadth-First Search, Union Find +2
0684	Redundant Connection	Medium	Depth-First Search, Breadth-First Search, Union Find +1
0323	Number of Connected Components in an Undirected GraphPremium	Medium	Depth-First Search, Breadth-First Search, Union Find +1
0261	Graph Valid TreePremium	Medium	Depth-First Search, Breadth-First Search, Union Find +1
1584	Min Cost to Connect All Points	Medium	Union Find, Graph, Array +1
0778	Swim in Rising Water	Hard	Depth-First Search, Breadth-First Search, Union Find +4

Two Pointers (8)

Two Pointers
No.	Problem	Difficulty	Topics
0125	Valid Palindrome	Easy	Two Pointers, String
0167	Two Sum II - Input Array Is Sorted	Medium	Array, Two Pointers, Binary Search
0015	3Sum	Medium	Array, Two Pointers, Sorting
0011	Container With Most Water	Medium	Greedy, Array, Two Pointers
0005	Longest Palindromic Substring	Medium	Two Pointers, String, Dynamic Programming
0647	Palindromic Substrings	Medium	Two Pointers, String, Dynamic Programming
0763	Partition Labels	Medium	Greedy, Hash Table, Two Pointers +1
0202	Happy Number	Easy	Hash Table, Math, Two Pointers

Stack (8)

Stack
No.	Problem	Difficulty	Topics
0042	Trapping Rain Water	Hard	Stack, Array, Two Pointers +2
0020	Valid Parentheses	Easy	Stack, String
0155	Min Stack	Medium	Stack, Design
0150	Evaluate Reverse Polish Notation	Medium	Stack, Array, Math
0739	Daily Temperatures	Medium	Stack, Array, Monotonic Stack
0853	Car Fleet	Medium	Stack, Array, Sorting +1
0084	Largest Rectangle in Histogram	Hard	Stack, Array, Monotonic Stack
0678	Valid Parenthesis String	Medium	Stack, Greedy, String +1

Dynamic Programming (18)

Dynamic Programming
No.	Problem	Difficulty	Topics
0121	Best Time to Buy and Sell Stock	Easy	Array, Dynamic Programming
0070	Climbing Stairs	Easy	Memoization, Math, Dynamic Programming
0746	Min Cost Climbing Stairs	Easy	Array, Dynamic Programming
0198	House Robber	Medium	Array, Dynamic Programming
0213	House Robber II	Medium	Array, Dynamic Programming
0091	Decode Ways	Medium	String, Dynamic Programming
0152	Maximum Product Subarray	Medium	Array, Dynamic Programming
0416	Partition Equal Subset Sum	Medium	Array, Dynamic Programming
0062	Unique Paths	Medium	Math, Dynamic Programming, Combinatorics
1143	Longest Common Subsequence	Medium	String, Dynamic Programming
0309	Best Time to Buy and Sell Stock with Cooldown	Medium	Array, Dynamic Programming
0518	Coin Change II	Medium	Array, Dynamic Programming
0097	Interleaving String	Medium	String, Dynamic Programming
0115	Distinct Subsequences	Hard	String, Dynamic Programming
0072	Edit Distance	Medium	String, Dynamic Programming
0312	Burst Balloons	Hard	Array, Dynamic Programming
0010	Regular Expression Matching	Hard	Recursion, String, Dynamic Programming
0053	Maximum Subarray	Medium	Array, Divide and Conquer, Dynamic Programming

Sliding Window (5)

Sliding Window
No.	Problem	Difficulty	Topics
0003	Longest Substring Without Repeating Characters	Medium	Hash Table, String, Sliding Window
0424	Longest Repeating Character Replacement	Medium	Hash Table, String, Sliding Window
0567	Permutation in String	Medium	Hash Table, Two Pointers, String +1
0076	Minimum Window Substring	Hard	Hash Table, String, Sliding Window
0239	Sliding Window Maximum	Hard	Queue, Array, Sliding Window +2

Backtracking (11)

Backtracking
No.	Problem	Difficulty	Topics
0022	Generate Parentheses	Medium	String, Dynamic Programming, Backtracking
0078	Subsets	Medium	Bit Manipulation, Array, Backtracking
0039	Combination Sum	Medium	Array, Backtracking
0046	Permutations	Medium	Array, Backtracking
0090	Subsets II	Medium	Bit Manipulation, Array, Backtracking
0040	Combination Sum II	Medium	Array, Backtracking
0079	Word Search	Medium	Depth-First Search, Array, String +2
0131	Palindrome Partitioning	Medium	String, Dynamic Programming, Backtracking
0017	Letter Combinations of a Phone Number	Medium	Hash Table, String, Backtracking
0051	N-Queens	Hard	Array, Backtracking
0494	Target Sum	Medium	Array, Dynamic Programming, Backtracking

Binary Search (7)

Binary Search
No.	Problem	Difficulty	Topics
0704	Binary Search	Easy	Array, Binary Search
0875	Koko Eating Bananas	Medium	Array, Binary Search
0153	Find Minimum in Rotated Sorted Array	Medium	Array, Binary Search
0033	Search in Rotated Sorted Array	Medium	Array, Binary Search
0981	Time Based Key-Value Store	Medium	Design, Hash Table, String +1
0004	Median of Two Sorted Arrays	Hard	Array, Binary Search, Divide and Conquer
0300	Longest Increasing Subsequence	Medium	Array, Binary Search, Dynamic Programming

Linked List (11)

Linked List
No.	Problem	Difficulty	Topics
0206	Reverse Linked List	Easy	Recursion, Linked List
0021	Merge Two Sorted Lists	Easy	Recursion, Linked List
0143	Reorder List	Medium	Stack, Recursion, Linked List +1
0019	Remove Nth Node From End of List	Medium	Linked List, Two Pointers
0138	Copy List with Random Pointer	Medium	Hash Table, Linked List
0002	Add Two Numbers	Medium	Recursion, Linked List, Math
0141	Linked List Cycle	Easy	Hash Table, Linked List, Two Pointers
0146	LRU Cache	Medium	Design, Hash Table, Linked List +1
0023	Merge k Sorted Lists	Hard	Linked List, Divide and Conquer, Heap (Priority Queue) +1
0025	Reverse Nodes in k-Group	Hard	Recursion, Linked List
0355	Design Twitter	Medium	Design, Hash Table, Linked List +1

Bit Manipulation (7)

Bit Manipulation
No.	Problem	Difficulty	Topics
0287	Find the Duplicate Number	Medium	Bit Manipulation, Array, Two Pointers +1
0136	Single Number	Easy	Bit Manipulation, Array
0191	Number of 1 Bits	Easy	Bit Manipulation, Divide and Conquer
0338	Counting Bits	Easy	Bit Manipulation, Dynamic Programming
0190	Reverse Bits	Easy	Bit Manipulation, Divide and Conquer
0268	Missing Number	Easy	Bit Manipulation, Array, Hash Table +3
0371	Sum of Two Integers	Medium	Bit Manipulation, Math

Tree Traversal (15)

Tree Traversal
No.	Problem	Difficulty	Topics
0226	Invert Binary Tree	Easy	Tree, Depth-First Search, Breadth-First Search +1
0104	Maximum Depth of Binary Tree	Easy	Tree, Depth-First Search, Breadth-First Search +1
0543	Diameter of Binary Tree	Easy	Tree, Depth-First Search, Binary Tree
0110	Balanced Binary Tree	Easy	Tree, Depth-First Search, Binary Tree
0100	Same Tree	Easy	Tree, Depth-First Search, Breadth-First Search +1
0572	Subtree of Another Tree	Easy	Tree, Depth-First Search, Binary Tree +2
0235	Lowest Common Ancestor of a Binary Search Tree	Medium	Tree, Depth-First Search, Binary Search Tree +1
0102	Binary Tree Level Order Traversal	Medium	Tree, Breadth-First Search, Binary Tree
0199	Binary Tree Right Side View	Medium	Tree, Depth-First Search, Breadth-First Search +1
1448	Count Good Nodes in Binary Tree	Medium	Tree, Depth-First Search, Breadth-First Search +1
0098	Validate Binary Search Tree	Medium	Tree, Depth-First Search, Binary Search Tree +1
0230	Kth Smallest Element in a BST	Medium	Tree, Depth-First Search, Binary Search Tree +1
0105	Construct Binary Tree from Preorder and Inorder Traversal	Medium	Tree, Array, Hash Table +2
0124	Binary Tree Maximum Path Sum	Hard	Tree, Depth-First Search, Dynamic Programming +1
0297	Serialize and Deserialize Binary Tree	Hard	Tree, Depth-First Search, Breadth-First Search +3

Trie (4)

Trie
No.	Problem	Difficulty	Topics
0208	Implement Trie (Prefix Tree)	Medium	Design, Trie, Hash Table +1
0211	Design Add and Search Words Data Structure	Medium	Depth-First Search, Design, Trie +1
0212	Word Search II	Hard	Trie, Array, String +2
0139	Word Break	Medium	Trie, Memoization, Array +3

Breadth-First Search (3)

Breadth-First Search
No.	Problem	Difficulty	Topics
0133	Clone Graph	Medium	Depth-First Search, Breadth-First Search, Graph +1
0127	Word Ladder	Hard	Breadth-First Search, Hash Table, String
0322	Coin Change	Medium	Breadth-First Search, Array, Dynamic Programming

Topological Sort (4)

Topological Sort
No.	Problem	Difficulty	Topics
0207	Course Schedule	Medium	Depth-First Search, Breadth-First Search, Graph +1
0210	Course Schedule II	Medium	Depth-First Search, Breadth-First Search, Graph +1
0269	Alien DictionaryPremium	Hard	Depth-First Search, Breadth-First Search, Graph +3
0329	Longest Increasing Path in a Matrix	Hard	Depth-First Search, Breadth-First Search, Graph +5

Depth-First Search (1)

Depth-First Search
No.	Problem	Difficulty	Topics
0332	Reconstruct Itinerary	Hard	Depth-First Search, Graph, Eulerian Circuit

Greedy (6)

Greedy
No.	Problem	Difficulty	Topics
0055	Jump Game	Medium	Greedy, Array, Dynamic Programming
0045	Jump Game II	Medium	Greedy, Array, Dynamic Programming
0846	Hand of Straights	Medium	Greedy, Array, Hash Table +1
1899	Merge Triplets to Form Target Triplet	Medium	Greedy, Array
0134	Gas Station	Medium	Greedy, Array
0435	Non-overlapping Intervals	Medium	Greedy, Array, Dynamic Programming +1

Math and Number Theory (4)

Math and Number Theory
No.	Problem	Difficulty	Topics
0066	Plus One	Easy	Array, Math
0050	Pow(x, n)	Medium	Recursion, Math
0043	Multiply Strings	Medium	Math, String, Simulation
0007	Reverse Integer	Medium	Math

The NeetCode 150 is a published third-party selection, reproduced here by problem number in the order the list itself uses. 143 of its 150 entries carry a complete Python solution; the other 7 are LeetCode Premium (marked in the tables) or have no usable solution in our dataset, and are listed rather than dropped.

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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.

Type your message...

GPT-6.1 Terra

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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

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

90%Subscription

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

Primary display

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

Other study lists

Or go by technique instead of by list: all LeetCode patterns · the full problem list.

Every entry, grouped by pattern

01Sorting (5)5

02Hash Map (2)2

03Heap / Priority Queue (10)10

04Other (2)2

05Prefix Sum (2)2

06Matrix and Grid (8)8

07Union-Find (9)9

08Two Pointers (8)8

09Stack (8)8

10Dynamic Programming (18)18

11Sliding Window (5)5

12Backtracking (11)11

13Binary Search (7)7

14Linked List (11)11

15Bit Manipulation (7)7

16Tree Traversal (15)15

17Trie (4)4

18Breadth-First Search (3)3

19Topological Sort (4)4

20Depth-First Search (1)1

21Greedy (6)6

22Math and Number Theory (4)4

The NeetCode 150 does not cover the problem you get asked.

Approach

Approach

Approach

Other study lists

Sorting (5)

Hash Map (2)

Heap / Priority Queue (10)

Other (2)

Prefix Sum (2)

Matrix and Grid (8)

Union-Find (9)

Two Pointers (8)

Stack (8)

Dynamic Programming (18)

Sliding Window (5)

Backtracking (11)

Binary Search (7)

Linked List (11)

Bit Manipulation (7)

Tree Traversal (15)

Trie (4)

Breadth-First Search (3)

Topological Sort (4)

Depth-First Search (1)

Greedy (6)

Math and Number Theory (4)