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Top Interview 150

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LeetCode's official plan, in its own topic groups. Pick it if you like practising inside LeetCode's study-plan page.

150 problems
39 easy · 93 medium · 18 hard
23 topic groups
no Premium problems

source: leetcode.com ↗ · read on 2026-10-13

Grouped the way Top Interview 150 groups it, in its own order. Tick a problem as solved on its page.

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Array / String

0 / 24 solved

not solved yet88
Merge Sorted Array
12 · Two Pointers
Easy
not solved yet27
Remove Element
12 · Two Pointers
Easy
not solved yet26
Remove Duplicates from Sorted Array
12 · Two Pointers
Easy
not solved yet80
Remove Duplicates from Sorted Array II
12 · Two Pointers
Medium
not solved yet169
Majority Element
10 · Arrays & Strings
Easy
not solved yet189
Rotate Array
10 · Arrays & Strings
Medium
not solved yet121
Best Time to Buy and Sell Stock
10 · Arrays & Strings
Easy
not solved yet122
Best Time to Buy and Sell Stock II
10 · Arrays & Strings
Medium
not solved yet55
Jump Game
32 · Greedy
Medium
not solved yet45
Jump Game II
32 · Greedy
Medium
not solved yet274
H-Index
19 · Sorting
Medium
not solved yet380
Insert Delete GetRandom O(1)
37 · Design DS
Medium
not solved yet238
Product of Array Except Self
10 · Arrays & Strings
Medium
not solved yet134
Gas Station
32 · Greedy
Medium
not solved yet135
Candy
32 · Greedy
Hard
not solved yet42
Trapping Rain Water
12 · Two Pointers
Hard
not solved yet13
Roman to Integer
20 · Parsing
Easy
not solved yet12
Integer to Roman
20 · Parsing
Medium
not solved yet58
Length of Last Word
02 · Java Arrays & Strings
Easy
not solved yet14
Longest Common Prefix
10 · Arrays & Strings
Easy
not solved yet151
Reverse Words in a String
20 · Parsing
Medium
not solved yet6
Zigzag Conversion
11 · Matrices
Medium
not solved yet28
Find the Index of the First Occurrence in a String
38 · Range Queries & Strings
Easy
not solved yet68
Text Justification
20 · Parsing
Hard

Two Pointers

0 / 5 solved

not solved yet125
Valid Palindrome
12 · Two Pointers
Easy
not solved yet392
Is Subsequence
12 · Two Pointers
Easy
not solved yet167
Two Sum II - Input Array Is Sorted
12 · Two Pointers
Medium
not solved yet11
Container With Most Water
12 · Two Pointers
Medium
not solved yet15
3Sum
12 · Two Pointers
Medium

Sliding Window

0 / 4 solved

not solved yet209
Minimum Size Subarray Sum
13 · Sliding Window
Medium
not solved yet3
Longest Substring Without Repeating Characters
13 · Sliding Window
Medium
not solved yet30
Substring with Concatenation of All Words
13 · Sliding Window
Hard
not solved yet76
Minimum Window Substring
13 · Sliding Window
Hard

Matrix

0 / 5 solved

not solved yet36
Valid Sudoku
14 · Hashing
Medium
not solved yet54
Spiral Matrix
11 · Matrices
Medium
not solved yet48
Rotate Image
11 · Matrices
Medium
not solved yet73
Set Matrix Zeroes
11 · Matrices
Medium
not solved yet289
Game of Life
11 · Matrices
Medium

Hashmap

0 / 9 solved

not solved yet383
Ransom Note
14 · Hashing
Easy
not solved yet205
Isomorphic Strings
14 · Hashing
Easy
not solved yet290
Word Pattern
14 · Hashing
Easy
not solved yet242
Valid Anagram
10 · Arrays & Strings
Easy
not solved yet49
Group Anagrams
10 · Arrays & Strings
Medium
not solved yet1
Two Sum
14 · Hashing
Easy
not solved yet202
Happy Number
09 · Math & Numbers
Easy
not solved yet219
Contains Duplicate II
13 · Sliding Window
Easy
not solved yet128
Longest Consecutive Sequence
14 · Hashing
Medium

Intervals

0 / 4 solved

not solved yet228
Summary Ranges
33 · Intervals
Easy
not solved yet56
Merge Intervals
33 · Intervals
Medium
not solved yet57
Insert Interval
33 · Intervals
Medium
not solved yet452
Minimum Number of Arrows to Burst Balloons
33 · Intervals
Medium

Stack

0 / 5 solved

not solved yet20
Valid Parentheses
16 · Stacks
Easy
not solved yet71
Simplify Path
16 · Stacks
Medium
not solved yet155
Min Stack
16 · Stacks
Medium
not solved yet150
Evaluate Reverse Polish Notation
16 · Stacks
Medium
not solved yet224
Basic Calculator
20 · Parsing
Hard

Linked List

0 / 11 solved

not solved yet141
Linked List Cycle
15 · Linked Lists
Easy
not solved yet2
Add Two Numbers
15 · Linked Lists
Medium
not solved yet21
Merge Two Sorted Lists
15 · Linked Lists
Easy
not solved yet138
Copy List with Random Pointer
15 · Linked Lists
Medium
not solved yet92
Reverse Linked List II
15 · Linked Lists
Medium
not solved yet25
Reverse Nodes in k-Group
15 · Linked Lists
Hard
not solved yet19
Remove Nth Node From End of List
15 · Linked Lists
Medium
not solved yet82
Remove Duplicates from Sorted List II
15 · Linked Lists
Medium
not solved yet61
Rotate List
15 · Linked Lists
Medium
not solved yet86
Partition List
15 · Linked Lists
Medium
not solved yet146
LRU Cache
15 · Linked Lists
Medium

Binary Tree General

0 / 14 solved

not solved yet104
Maximum Depth of Binary Tree
22 · Tree Recursion
Easy
not solved yet100
Same Tree
22 · Tree Recursion
Easy
not solved yet226
Invert Binary Tree
22 · Tree Recursion
Easy
not solved yet101
Symmetric Tree
22 · Tree Recursion
Easy
not solved yet105
Construct Binary Tree from Preorder and Inorder Traversal
22 · Tree Recursion
Medium
not solved yet106
Construct Binary Tree from Inorder and Postorder Traversal
22 · Tree Recursion
Medium
not solved yet117
Populating Next Right Pointers in Each Node II
21 · Traversals
Medium
not solved yet114
Flatten Binary Tree to Linked List
22 · Tree Recursion
Medium
not solved yet112
Path Sum
22 · Tree Recursion
Easy
not solved yet129
Sum Root to Leaf Numbers
22 · Tree Recursion
Medium
not solved yet124
Binary Tree Maximum Path Sum
22 · Tree Recursion
Hard
not solved yet173
Binary Search Tree Iterator
23 · BST
Medium
not solved yet222
Count Complete Tree Nodes
22 · Tree Recursion
Medium
not solved yet236
Lowest Common Ancestor of a Binary Tree
22 · Tree Recursion
Medium

Binary Tree BFS

0 / 4 solved

not solved yet199
Binary Tree Right Side View
21 · Traversals
Medium
not solved yet637
Average of Levels in Binary Tree
21 · Traversals
Easy
not solved yet102
Binary Tree Level Order Traversal
21 · Traversals
Medium
not solved yet103
Binary Tree Zigzag Level Order Traversal
21 · Traversals
Medium

Binary Search Tree

0 / 3 solved

not solved yet530
Minimum Absolute Difference in BST
23 · BST
Easy
not solved yet230
Kth Smallest Element in a BST
23 · BST
Medium
not solved yet98
Validate Binary Search Tree
23 · BST
Medium

Graph General

0 / 6 solved

not solved yet200
Number of Islands
26 · Graphs
Medium
not solved yet130
Surrounded Regions
26 · Graphs
Medium
not solved yet133
Clone Graph
26 · Graphs
Medium
not solved yet399
Evaluate Division
30 · Advanced Graphs
Medium
not solved yet207
Course Schedule
29 · Topo Sort
Medium
not solved yet210
Course Schedule II
29 · Topo Sort
Medium

Graph BFS

0 / 3 solved

not solved yet909
Snakes and Ladders
26 · Graphs
Medium
not solved yet433
Minimum Genetic Mutation
26 · Graphs
Medium
not solved yet127
Word Ladder
26 · Graphs
Hard

Trie

0 / 3 solved

not solved yet208
Implement Trie (Prefix Tree)
25 · Tries
Medium
not solved yet211
Design Add and Search Words Data Structure
25 · Tries
Medium
not solved yet212
Word Search II
25 · Tries
Hard

Backtracking

0 / 7 solved

not solved yet17
Letter Combinations of a Phone Number
31 · Backtracking
Medium
not solved yet77
Combinations
31 · Backtracking
Medium
not solved yet46
Permutations
31 · Backtracking
Medium
not solved yet39
Combination Sum
31 · Backtracking
Medium
not solved yet52
N-Queens II
31 · Backtracking
Hard
not solved yet22
Generate Parentheses
31 · Backtracking
Medium
not solved yet79
Word Search
31 · Backtracking
Medium

Divide & Conquer

0 / 4 solved

not solved yet108
Convert Sorted Array to Binary Search Tree
23 · BST
Easy
not solved yet148
Sort List
19 · Sorting
Medium
not solved yet427
Construct Quad Tree
08 · Recursion
Medium
not solved yet23
Merge k Sorted Lists
24 · Heaps
Hard

Kadane's Algorithm

0 / 2 solved

not solved yet53
Maximum Subarray
10 · Arrays & Strings
Medium
not solved yet918
Maximum Sum Circular Subarray
10 · Arrays & Strings
Medium

Binary Search

0 / 7 solved

not solved yet35
Search Insert Position
18 · Binary Search
Easy
not solved yet74
Search a 2D Matrix
18 · Binary Search
Medium
not solved yet162
Find Peak Element
18 · Binary Search
Medium
not solved yet33
Search in Rotated Sorted Array
18 · Binary Search
Medium
not solved yet34
Find First and Last Position of Element in Sorted Array
18 · Binary Search
Medium
not solved yet153
Find Minimum in Rotated Sorted Array
18 · Binary Search
Medium
not solved yet4
Median of Two Sorted Arrays
18 · Binary Search
Hard

Heap

0 / 4 solved

not solved yet215
Kth Largest Element in an Array
24 · Heaps
Medium
not solved yet502
IPO
24 · Heaps
Hard
not solved yet373
Find K Pairs with Smallest Sums
24 · Heaps
Medium
not solved yet295
Find Median from Data Stream
24 · Heaps
Hard

Bit Manipulation

0 / 6 solved

not solved yet67
Add Binary
34 · Bits
Easy
not solved yet190
Reverse Bits
34 · Bits
Easy
not solved yet191
Number of 1 Bits
34 · Bits
Easy
not solved yet136
Single Number
34 · Bits
Easy
not solved yet137
Single Number II
34 · Bits
Medium
not solved yet201
Bitwise AND of Numbers Range
34 · Bits
Medium

Math

0 / 6 solved

not solved yet9
Palindrome Number
09 · Math & Numbers
Easy
not solved yet66
Plus One
09 · Math & Numbers
Easy
not solved yet172
Factorial Trailing Zeroes
09 · Math & Numbers
Medium
not solved yet69
Sqrt(x)
07 · Big-O
Easy
not solved yet50
Pow(x, n)
08 · Recursion
Medium
not solved yet149
Max Points on a Line
09 · Math & Numbers
Hard

1D DP

0 / 5 solved

not solved yet70
Climbing Stairs
35 · Dynamic Programming
Easy
not solved yet198
House Robber
35 · Dynamic Programming
Medium
not solved yet139
Word Break
35 · Dynamic Programming
Medium
not solved yet322
Coin Change
35 · Dynamic Programming
Medium
not solved yet300
Longest Increasing Subsequence
35 · Dynamic Programming
Medium

Multidimensional DP

0 / 9 solved

not solved yet120
Triangle
35 · Dynamic Programming
Medium
not solved yet64
Minimum Path Sum
35 · Dynamic Programming
Medium
not solved yet63
Unique Paths II
35 · Dynamic Programming
Medium
not solved yet5
Longest Palindromic Substring
35 · Dynamic Programming
Medium
not solved yet97
Interleaving String
36 · DP Patterns
Medium
not solved yet72
Edit Distance
35 · Dynamic Programming
Medium
not solved yet123
Best Time to Buy and Sell Stock III
36 · DP Patterns
Hard
not solved yet188
Best Time to Buy and Sell Stock IV
36 · DP Patterns
Hard
not solved yet221
Maximal Square
35 · Dynamic Programming
Medium