The Blind 75 LeetCode List

The Blind 75: a 75-problem list assembled from the patterns that keep reappearing in technical interviews, grouped by topic. Every entry links to a Python solution with complexity analysis.

75 problems
19 Easy
49 Medium
7 Hard
20 patterns

Where this list comes from

The Blind 75 is not ours. It is a published selection that people work through by name, and we reproduce it here by problem number, in the order the list itself uses. What we add is the solution: of the 75 entries below, 69 carry a complete Python solution with a worked example and its time and space complexity. The remaining 6 are either LeetCode Premium problems, whose statements are paywalled at the source, or problems our dataset holds no usable solution for. They are listed rather than quietly dropped, and the premium ones are marked in the tables.

The published list names 75 entries. All 75 resolve to a problem in this library and are listed below.

Every count on this page is computed from what the page renders, so the number in a heading is the number of rows under it. Nothing is padded to make a title's number come out right — that would be wrong in a way anyone who knows the list would spot in seconds.

All 75 problems, 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.

Hash Map (2)

#	Problem	Difficulty	Topics
1	Two Sum	Easy	Array, Hash Table
271	Encode and Decode StringsPremium	Medium	Design, Array, String

Dynamic Programming (10)

#	Problem	Difficulty	Topics
121	Best Time to Buy and Sell Stock	Easy	Array, Dynamic Programming
53	Maximum Subarray	Medium	Array, Divide and Conquer, Dynamic Programming
152	Maximum Product Subarray	Medium	Array, Dynamic Programming
70	Climbing Stairs	Easy	Memoization, Math, Dynamic Programming
1143	Longest Common Subsequence	Medium	String, Dynamic Programming
377	Combination Sum IV	Medium	Array, Dynamic Programming
198	House Robber	Medium	Array, Dynamic Programming
213	House Robber II	Medium	Array, Dynamic Programming
91	Decode Ways	Medium	String, Dynamic Programming
62	Unique Paths	Medium	Math, Dynamic Programming, Combinatorics

Sorting (5)

#	Problem	Difficulty	Topics
217	Contains Duplicate	Easy	Array, Hash Table, Sorting
56	Merge Intervals	Medium	Array, Sorting
252	Meeting RoomsPremium	Easy	Array, Sorting
242	Valid Anagram	Easy	Hash Table, String, Sorting
49	Group Anagrams	Medium	Array, Hash Table, String +1

Prefix Sum (2)

#	Problem	Difficulty	Topics
238	Product of Array Except Self	Medium	Array, Prefix Sum
253	Meeting Rooms IIPremium	Medium	Greedy, Array, Two Pointers +3

Monotonic Stack (3)

#	Problem	Difficulty	Topics
153	Find Minimum in Rotated Sorted Array	Medium	Array, Binary Search
33	Search in Rotated Sorted Array	Medium	Array, Binary Search
300	Longest Increasing Subsequence	Medium	Array, Binary Search, Dynamic Programming

Two Pointers (5)

#	Problem	Difficulty	Topics
15	3Sum	Medium	Array, Two Pointers, Sorting
11	Container With Most Water	Medium	Greedy, Array, Two Pointers
125	Valid Palindrome	Easy	Two Pointers, String
5	Longest Palindromic Substring	Medium	Two Pointers, String, Dynamic Programming
647	Palindromic Substrings	Medium	Two Pointers, String, Dynamic Programming

Bit Manipulation (5)

#	Problem	Difficulty	Topics
371	Sum of Two Integers	Medium	Bit Manipulation, Math
191	Number of 1 Bits	Easy	Bit Manipulation, Divide and Conquer
338	Counting Bits	Easy	Bit Manipulation, Dynamic Programming
268	Missing Number	Easy	Bit Manipulation, Array, Hash Table +3
190	Reverse Bits	Easy	Bit Manipulation, Divide and Conquer

Breadth-First Search (2)

#	Problem	Difficulty	Topics
322	Coin Change	Medium	Breadth-First Search, Array, Dynamic Programming
133	Clone Graph	Medium	Depth-First Search, Breadth-First Search, Graph +1

Trie (4)

#	Problem	Difficulty	Topics
139	Word Break	Medium	Trie, Memoization, Array +3
208	Implement Trie (Prefix Tree)	Medium	Design, Trie, Hash Table +1
211	Design Add and Search Words Data Structure	Medium	Depth-First Search, Design, Trie +1
212	Word Search II	Hard	Trie, Array, String +2

Greedy (2)

#	Problem	Difficulty	Topics
55	Jump Game	Medium	Greedy, Array, Dynamic Programming
435	Non-overlapping Intervals	Medium	Greedy, Array, Dynamic Programming +1

Topological Sort (2)

#	Problem	Difficulty	Topics
207	Course Schedule	Medium	Depth-First Search, Breadth-First Search, Graph +1
269	Alien DictionaryPremium	Hard	Depth-First Search, Breadth-First Search, Graph +3

Matrix and Grid (4)

#	Problem	Difficulty	Topics
417	Pacific Atlantic Water Flow	Medium	Depth-First Search, Breadth-First Search, Array +1
73	Set Matrix Zeroes	Medium	Array, Hash Table, Matrix
54	Spiral Matrix	Medium	Array, Matrix, Simulation
48	Rotate Image	Medium	Array, Math, Matrix

Union-Find (4)

#	Problem	Difficulty	Topics
200	Number of Islands	Medium	Depth-First Search, Breadth-First Search, Union Find +2
128	Longest Consecutive Sequence	Medium	Union Find, Array, Hash Table
261	Graph Valid TreePremium	Medium	Depth-First Search, Breadth-First Search, Union Find +1
323	Number of Connected Components in an Undirected GraphPremium	Medium	Depth-First Search, Breadth-First Search, Union Find +1

Other (1)

#	Problem	Difficulty	Topics
57	Insert Interval	Medium	Array

Linked List (6)

#	Problem	Difficulty	Topics
206	Reverse Linked List	Easy	Recursion, Linked List
141	Linked List Cycle	Easy	Hash Table, Linked List, Two Pointers
21	Merge Two Sorted Lists	Easy	Recursion, Linked List
23	Merge k Sorted Lists	Hard	Linked List, Divide and Conquer, Heap (Priority Queue) +1
19	Remove Nth Node From End of List	Medium	Linked List, Two Pointers
143	Reorder List	Medium	Stack, Recursion, Linked List +1

Backtracking (1)

#	Problem	Difficulty	Topics
79	Word Search	Medium	Depth-First Search, Array, String +2

Sliding Window (3)

#	Problem	Difficulty	Topics
3	Longest Substring Without Repeating Characters	Medium	Hash Table, String, Sliding Window
424	Longest Repeating Character Replacement	Medium	Hash Table, String, Sliding Window
76	Minimum Window Substring	Hard	Hash Table, String, Sliding Window

Stack (1)

#	Problem	Difficulty	Topics
20	Valid Parentheses	Easy	Stack, String

Tree Traversal (11)

#	Problem	Difficulty	Topics
104	Maximum Depth of Binary Tree	Easy	Tree, Depth-First Search, Breadth-First Search +1
100	Same Tree	Easy	Tree, Depth-First Search, Breadth-First Search +1
226	Invert Binary Tree	Easy	Tree, Depth-First Search, Breadth-First Search +1
124	Binary Tree Maximum Path Sum	Hard	Tree, Depth-First Search, Dynamic Programming +1
102	Binary Tree Level Order Traversal	Medium	Tree, Breadth-First Search, Binary Tree
297	Serialize and Deserialize Binary Tree	Hard	Tree, Depth-First Search, Breadth-First Search +3
572	Subtree of Another Tree	Easy	Tree, Depth-First Search, Binary Tree +2
105	Construct Binary Tree from Preorder and Inorder Traversal	Medium	Tree, Array, Hash Table +2
98	Validate Binary Search Tree	Medium	Tree, Depth-First Search, Binary Search Tree +1
230	Kth Smallest Element in a BST	Medium	Tree, Depth-First Search, Binary Search Tree +1
235	Lowest Common Ancestor of a Binary Search Tree	Medium	Tree, Depth-First Search, Binary Search Tree +1

Heap / Priority Queue (2)

#	Problem	Difficulty	Topics
347	Top K Frequent Elements	Medium	Array, Hash Table, Divide and Conquer +5
295	Find Median from Data Stream	Hard	Design, Two Pointers, Data Stream +2

Other study lists

NeetCode 150150 problemsThe NeetCode 150: an expansion of the Blind 75 into eighteen topic groups, from arrays and hashing through advanced graphs and two-dimensional dynamic programming.Grind 7575 problemsThe Grind 75: the Blind 75 reworked into a week-by-week schedule that starts with the easiest high-yield problems and ends on the hard ones. Ordered for study, not by topic.LeetCode 7575 problemsLeetCode 75: the official study plan, seventy-five problems across twenty-two topic groups from array and string work up to monotonic stacks. Skewed easier than the Blind 75 and better as a first pass.Top Interview 150150 problemsTop Interview 150: the official interview-preparation list, a hundred and fifty problems covering every data structure and technique a technical screen is likely to reach for.

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

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