The Grind 75 LeetCode List

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.

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Easy: 23
Medium: 43
Hard: 9
Patterns: 20

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.

Hash Map (2)

Hash Map
No.	Problem	Difficulty	Topics
0001	Two Sum	Easy	Array, Hash Table
0383	Ransom Note	Easy	Hash Table, String, Counting

Stack (7)

Stack
No.	Problem	Difficulty	Topics
0020	Valid Parentheses	Easy	Stack, String
0232	Implement Queue using Stacks	Easy	Stack, Design, Queue
0150	Evaluate Reverse Polish Notation	Medium	Stack, Array, Math
0155	Min Stack	Medium	Stack, Design
0042	Trapping Rain Water	Hard	Stack, Array, Two Pointers +2
0224	Basic Calculator	Hard	Stack, Recursion, Math +1
0084	Largest Rectangle in Histogram	Hard	Stack, Array, Monotonic Stack

Linked List (6)

Linked List
No.	Problem	Difficulty	Topics
0021	Merge Two Sorted Lists	Easy	Recursion, Linked List
0141	Linked List Cycle	Easy	Hash Table, Linked List, Two Pointers
0206	Reverse Linked List	Easy	Recursion, Linked List
0876	Middle of the Linked List	Easy	Linked List, Two Pointers
0023	Merge k Sorted Lists	Hard	Linked List, Divide and Conquer, Heap (Priority Queue) +1
0146	LRU Cache	Medium	Design, Hash Table, Linked List +1

Dynamic Programming (5)

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
0053	Maximum Subarray	Medium	Array, Divide and Conquer, Dynamic Programming
0416	Partition Equal Subset Sum	Medium	Array, Dynamic Programming
0062	Unique Paths	Medium	Math, Dynamic Programming, Combinatorics

Two Pointers (5)

Two Pointers
No.	Problem	Difficulty	Topics
0125	Valid Palindrome	Easy	Two Pointers, String
0015	3Sum	Medium	Array, Two Pointers, Sorting
0075	Sort Colors	Medium	Array, Two Pointers, Sorting
0005	Longest Palindromic Substring	Medium	Two Pointers, String, Dynamic Programming
0011	Container With Most Water	Medium	Greedy, Array, Two Pointers

Tree Traversal (12)

Tree Traversal
No.	Problem	Difficulty	Topics
0226	Invert Binary Tree	Easy	Tree, Depth-First Search, Breadth-First Search +1
0235	Lowest Common Ancestor of a Binary Search Tree	Medium	Tree, Depth-First Search, Binary Search Tree +1
0110	Balanced Binary Tree	Easy	Tree, Depth-First Search, Binary Tree
0543	Diameter of Binary Tree	Easy	Tree, Depth-First Search, Binary Tree
0104	Maximum Depth of Binary Tree	Easy	Tree, Depth-First Search, Breadth-First Search +1
0102	Binary Tree Level Order Traversal	Medium	Tree, Breadth-First Search, Binary Tree
0098	Validate Binary Search Tree	Medium	Tree, Depth-First Search, Binary Search Tree +1
0236	Lowest Common Ancestor of a Binary Tree	Medium	Tree, Depth-First Search, Binary Tree
0199	Binary Tree Right Side View	Medium	Tree, Depth-First Search, Breadth-First Search +1
0105	Construct Binary Tree from Preorder and Inorder Traversal	Medium	Tree, Array, Hash Table +2
0230	Kth Smallest Element in a BST	Medium	Tree, Depth-First Search, Binary Search Tree +1
0297	Serialize and Deserialize Binary Tree	Hard	Tree, Depth-First Search, Breadth-First Search +3

Sorting (4)

Sorting
No.	Problem	Difficulty	Topics
0242	Valid Anagram	Easy	Hash Table, String, Sorting
0169	Majority Element	Easy	Array, Hash Table, Divide and Conquer +2
0217	Contains Duplicate	Easy	Array, Hash Table, Sorting
0056	Merge Intervals	Medium	Array, Sorting

Binary Search (5)

Binary Search
No.	Problem	Difficulty	Topics
0704	Binary Search	Easy	Array, Binary Search
0278	First Bad Version	Easy	Binary Search, Interactive
0033	Search in Rotated Sorted Array	Medium	Array, Binary Search
0981	Time Based Key-Value Store	Medium	Design, Hash Table, String +1
1235	Maximum Profit in Job Scheduling	Hard	Array, Binary Search, Dynamic Programming +1

Matrix and Grid (4)

Matrix and Grid
No.	Problem	Difficulty	Topics
0733	Flood Fill	Easy	Depth-First Search, Breadth-First Search, Array +1
0542	01 Matrix	Medium	Breadth-First Search, Array, Dynamic Programming +1
0994	Rotting Oranges	Medium	Breadth-First Search, Array, Matrix
0054	Spiral Matrix	Medium	Array, Matrix, Simulation

Greedy (1)

Greedy
No.	Problem	Difficulty	Topics
0409	Longest Palindrome	Easy	Greedy, Hash Table, String

Bit Manipulation (1)

Bit Manipulation
No.	Problem	Difficulty	Topics
0067	Add Binary	Easy	Bit Manipulation, Math, String +1

Other (2)

Other
No.	Problem	Difficulty	Topics
0057	Insert Interval	Medium	Array
0008	String to Integer (atoi)	Medium	String

Heap / Priority Queue (3)

Heap / Priority Queue
No.	Problem	Difficulty	Topics
0973	K Closest Points to Origin	Medium	Geometry, Array, Math +4
0621	Task Scheduler	Medium	Greedy, Array, Hash Table +3
0295	Find Median from Data Stream	Hard	Design, Two Pointers, Data Stream +2

Sliding Window (3)

Sliding Window
No.	Problem	Difficulty	Topics
0003	Longest Substring Without Repeating Characters	Medium	Hash Table, String, Sliding Window
0438	Find All Anagrams in a String	Medium	Hash Table, String, Sliding Window
0076	Minimum Window Substring	Hard	Hash Table, String, Sliding Window

Breadth-First Search (3)

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

Topological Sort (2)

Topological Sort
No.	Problem	Difficulty	Topics
0207	Course Schedule	Medium	Depth-First Search, Breadth-First Search, Graph +1
0310	Minimum Height Trees	Medium	Depth-First Search, Breadth-First Search, Graph +1

Trie (2)

Trie
No.	Problem	Difficulty	Topics
0208	Implement Trie (Prefix Tree)	Medium	Design, Trie, Hash Table +1
0139	Word Break	Medium	Trie, Memoization, Array +3

Prefix Sum (1)

Prefix Sum
No.	Problem	Difficulty	Topics
0238	Product of Array Except Self	Medium	Array, Prefix Sum

Union-Find (2)

Union-Find
No.	Problem	Difficulty	Topics
0200	Number of Islands	Medium	Depth-First Search, Breadth-First Search, Union Find +2
0721	Accounts Merge	Medium	Depth-First Search, Breadth-First Search, Union Find +4

Backtracking (5)

Backtracking
No.	Problem	Difficulty	Topics
0039	Combination Sum	Medium	Array, Backtracking
0046	Permutations	Medium	Array, Backtracking
0078	Subsets	Medium	Bit Manipulation, Array, Backtracking
0017	Letter Combinations of a Phone Number	Medium	Hash Table, String, Backtracking
0079	Word Search	Medium	Depth-First Search, Array, String +2

The Grind 75 is a published third-party selection, reproduced here by problem number in the order the list itself uses. 75 of its 75 entries carry a complete Python solution.

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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...

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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

01Hash Map (2)2

02Stack (7)7

03Linked List (6)6

04Dynamic Programming (5)5

05Two Pointers (5)5

06Tree Traversal (12)12

07Sorting (4)4

08Binary Search (5)5

09Matrix and Grid (4)4

10Greedy (1)1

11Bit Manipulation (1)1

12Other (2)2

13Heap / Priority Queue (3)3

14Sliding Window (3)3

15Breadth-First Search (3)3

16Topological Sort (2)2

17Trie (2)2

18Prefix Sum (1)1

19Union-Find (2)2

20Backtracking (5)5

The Grind 75 does not cover the problem you get asked.

Approach

Approach

Approach

Other study lists

Hash Map (2)

Stack (7)

Linked List (6)

Dynamic Programming (5)

Two Pointers (5)

Tree Traversal (12)

Sorting (4)

Binary Search (5)

Matrix and Grid (4)

Greedy (1)

Bit Manipulation (1)

Other (2)

Heap / Priority Queue (3)

Sliding Window (3)

Breadth-First Search (3)

Topological Sort (2)

Trie (2)

Prefix Sum (1)

Union-Find (2)

Backtracking (5)