Solutions & Explanations

Browse 4,029+ detailed solutions with multiple approaches, code in Python, Java, C++ and more.

4,029 Solutions961 Easy2102 Medium966 Hard

Title	Difficulty	Acceptance	Topics	Solution
3313. Find the Last Marked Nodes in Tree	Hard	57.1%	Depth-First Search Tree	Read
3317. Find the Number of Possible Ways for an Event	Hard	34.8%	Combinatorics Dynamic Programming+1	Read
3320. Count The Number of Winning Sequences	Hard	32.4%	Dynamic Programming String	Read
3321. Find X-Sum of All K-Long Subarrays II	Hard	41.1%	Array Hash Table+2	Read
3327. Check if DFS Strings Are Palindromes	Hard	20.9%	Array Depth-First Search+4	Read
3329. Count Substrings With K-Frequency Characters II	Hard	72.2%	Hash Table Sliding Window+1	Read
3333. Find the Original Typed String II	Hard	45.6%	Dynamic Programming Prefix Sum+1	Read
3336. Find the Number of Subsequences With Equal GCD	Hard	66.7%	Array Dynamic Programming+2	Read
3337. Total Characters in String After Transformations II	Hard	58.0%	Counting Dynamic Programming+3	Read
3343. Count Number of Balanced Permutations	Hard	49.1%	Combinatorics Dynamic Programming+2	Read
3347. Maximum Frequency of an Element After Performing Operations II	Hard	53.8%	Array Binary Search+3	Read
3348. Smallest Divisible Digit Product II	Hard	45.3%	Backtracking Greedy+3	Read
3351. Sum of Good Subsequences	Hard	30.9%	Array Dynamic Programming+1	Read
3352. Count K-Reducible Numbers Less Than N	Hard	27.8%	Combinatorics Dynamic Programming+2	Read
3357. Minimize the Maximum Adjacent Element Difference	Hard	20.2%	Array Binary Search+1	Read
3359. Find Sorted Submatrices With Maximum Element at Most K	Hard	51.9%	Array Matrix+2	Read
3363. Find the Maximum Number of Fruits Collected	Hard	65.1%	Array Dynamic Programming+1	Read
3367. Maximize Sum of Weights after Edge Removals	Hard	31.9%	Depth-First Search Dynamic Programming+2	Read
3368. First Letter Capitalization	Hard	87.7%	Database	Read
3369. Design an Array Statistics Tracker	Hard	35.7%	Binary Search Hash Table+1	Read
3373. Maximize the Number of Target Nodes After Connecting Trees II	Hard	72.5%	Breadth-First Search Depth-First Search+1	Read
3374. First Letter Capitalization II	Hard	90.0%	Database	Read
3873. Maximum Points Activated with One Addition	Hard	42.8%	Array Hash Table+1	Read
3855. Sum of K-Digit Numbers in a Range	Hard	50.5%	Combinatorics Divide and Conquer+2	Read
3878. Count Good Subarrays	Hard	25.6%	Array Bit Manipulation+2	Read
3841. Palindromic Path Queries in a Tree	Hard	36.7%	Array Divide and Conquer+3	Read
3845. Maximum Subarray XOR with Bounded Range	Hard	32.3%	Array Bit Manipulation+5	Read
3836. Maximum Score Using Exactly K Pairs	Hard	41.4%	Array Dynamic Programming	Read
3830. Longest Alternating Subarray After Removing At Most One Element	Hard	30.9%	Array Dynamic Programming+1	Read
3864. Minimum Cost to Partition a Binary String	Hard	50.5%	Divide and Conquer Prefix Sum+1	Read
3821. Find Nth Smallest Integer With K One Bits	Hard	34.7%	Bit Manipulation Combinatorics+1	Read
3812. Minimum Edge Toggles on a Tree	Hard	65.6%	Depth-First Search Graph+3	Read
3782. Last Remaining Integer After Alternating Deletion Operations	Hard	49.2%	Math Recursion	Read
3869. Count Fancy Numbers in a Range	Hard	26.6%	Dynamic Programming Math	Read
3806. Maximum Bitwise AND After Increment Operations	Hard	31.9%	Array Bit Manipulation+2	Read
3797. Count Routes to Climb a Rectangular Grid	Hard	25.5%	Array Dynamic Programming+2	Read
3772. Maximum Subgraph Score in a Tree	Hard	65.4%	Array Depth-First Search+2	Read
3768. Minimum Inversion Count in Subarrays of Fixed Length	Hard	40.3%	Array Segment Tree+1	Read
3801. Minimum Cost to Merge Sorted Lists	Hard	33.2%	Array Binary Search+3	Read
3749. Evaluate Valid Expressions	Hard	69.4%	Divide and Conquer Hash Table+3	Read
3757. Number of Effective Subsequences	Hard	32.4%	Array Bit Manipulation+3	Read
3802. Number of Ways to Paint Sheets	Hard	67.3%		Read
3753. Total Waviness of Numbers in Range II	Hard	56.2%	Dynamic Programming Math	Read
3826. Minimum Partition Score	Hard	32.6%	Array Divide and Conquer+4	Read
3748. Count Stable Subarrays	Hard	33.0%	Array Binary Search+1	Read
3735. Lexicographically Smallest String After Reverse II	Hard	48.3%	Binary Search Hash Function+3	Read
3791. Number of Balanced Integers in a Range	Hard	36.3%	Dynamic Programming	Read
3816. Lexicographically Smallest String After Deleting Duplicate Characters	Hard	20.9%	Greedy Hash Table+3	Read
3739. Count Subarrays With Majority Element II	Hard	65.2%	Array Divide and Conquer+4	Read
3786. Total Sum of Interaction Cost in Tree Groups	Hard	54.3%	Array Depth-First Search+1	Read

#3313Hard

Find the Last Marked Nodes in Tree

Depth-First SearchTree

Acceptance: 57.1%

#3317Hard

Find the Number of Possible Ways for an Event

CombinatoricsDynamic ProgrammingMath

Acceptance: 34.8%

#3320Hard

Count The Number of Winning Sequences

Dynamic ProgrammingString

Acceptance: 32.4%

#3321Hard

Find X-Sum of All K-Long Subarrays II

ArrayHash TableHeap (Priority Queue)+1

Acceptance: 41.1%

#3327Hard

Check if DFS Strings Are Palindromes

ArrayDepth-First SearchHash Function+3

Acceptance: 20.9%

#3329Hard

Count Substrings With K-Frequency Characters II

Hash TableSliding WindowString

Acceptance: 72.2%

#3333Hard

Find the Original Typed String II

Dynamic ProgrammingPrefix SumString

Acceptance: 45.6%

#3336Hard

Find the Number of Subsequences With Equal GCD

ArrayDynamic ProgrammingMath+1

Acceptance: 66.7%

#3337Hard

Total Characters in String After Transformations II

CountingDynamic ProgrammingHash Table+2

Acceptance: 58.0%

#3343Hard

Count Number of Balanced Permutations

CombinatoricsDynamic ProgrammingMath+1

Acceptance: 49.1%

#3347Hard

Maximum Frequency of an Element After Performing Operations II

ArrayBinary SearchPrefix Sum+2

Acceptance: 53.8%

#3348Hard

Smallest Divisible Digit Product II

BacktrackingGreedyMath+2

Acceptance: 45.3%

#3351Hard

Sum of Good Subsequences

ArrayDynamic ProgrammingHash Table

Acceptance: 30.9%

#3352Hard

Count K-Reducible Numbers Less Than N

CombinatoricsDynamic ProgrammingMath+1

Acceptance: 27.8%

#3357Hard

Minimize the Maximum Adjacent Element Difference

ArrayBinary SearchGreedy

Acceptance: 20.2%

#3359Hard

Find Sorted Submatrices With Maximum Element at Most K

ArrayMatrixMonotonic Stack+1

Acceptance: 51.9%

#3363Hard

Find the Maximum Number of Fruits Collected

ArrayDynamic ProgrammingMatrix

Acceptance: 65.1%

#3367Hard

Maximize Sum of Weights after Edge Removals

Depth-First SearchDynamic ProgrammingSorting+1

Acceptance: 31.9%

#3368Hard

First Letter Capitalization

Database

Acceptance: 87.7%

#3369Hard

Design an Array Statistics Tracker

Binary SearchHash TableQueue

Acceptance: 35.7%

#3373Hard

Maximize the Number of Target Nodes After Connecting Trees II

Breadth-First SearchDepth-First SearchTree

Acceptance: 72.5%

#3374Hard

First Letter Capitalization II

Database

Acceptance: 90.0%

#3873Hard

Maximum Points Activated with One Addition

ArrayHash TableUnion Find

Acceptance: 42.8%

#3855Hard

Sum of K-Digit Numbers in a Range

CombinatoricsDivide and ConquerMath+1

Acceptance: 50.5%

#3878Hard

Count Good Subarrays

ArrayBit ManipulationMonotonic Stack+1

Acceptance: 25.6%

#3841Hard

Palindromic Path Queries in a Tree

ArrayDivide and ConquerSegment Tree+2

Acceptance: 36.7%

#3845Hard

Maximum Subarray XOR with Bounded Range

ArrayBit ManipulationMonotonic Queue+4

Acceptance: 32.3%

#3836Hard

Maximum Score Using Exactly K Pairs

ArrayDynamic Programming

Acceptance: 41.4%

#3830Hard

Longest Alternating Subarray After Removing At Most One Element

ArrayDynamic ProgrammingEnumeration

Acceptance: 30.9%

#3864Hard

Minimum Cost to Partition a Binary String

Divide and ConquerPrefix SumString

Acceptance: 50.5%

#3821Hard

Find Nth Smallest Integer With K One Bits

Bit ManipulationCombinatoricsMath

Acceptance: 34.7%

#3812Hard

Minimum Edge Toggles on a Tree

Depth-First SearchGraphSorting+2

Acceptance: 65.6%

#3782Hard

Last Remaining Integer After Alternating Deletion Operations

MathRecursion

Acceptance: 49.2%

#3869Hard

Count Fancy Numbers in a Range

Dynamic ProgrammingMath

Acceptance: 26.6%

#3806Hard

Maximum Bitwise AND After Increment Operations

ArrayBit ManipulationGreedy+1

Acceptance: 31.9%

#3797Hard

Count Routes to Climb a Rectangular Grid

ArrayDynamic ProgrammingMatrix+1

Acceptance: 25.5%

#3772Hard

Maximum Subgraph Score in a Tree

ArrayDepth-First SearchDynamic Programming+1

Acceptance: 65.4%

#3768Hard

Minimum Inversion Count in Subarrays of Fixed Length

ArraySegment TreeSliding Window

Acceptance: 40.3%

#3801Hard

Minimum Cost to Merge Sorted Lists

ArrayBinary SearchBit Manipulation+2

Acceptance: 33.2%

#3749Hard

Evaluate Valid Expressions

Divide and ConquerHash TableMath+2

Acceptance: 69.4%

#3757Hard

Number of Effective Subsequences

ArrayBit ManipulationCombinatorics+2

Acceptance: 32.4%

#3802Hard

Number of Ways to Paint Sheets

Acceptance: 67.3%

#3753Hard

Total Waviness of Numbers in Range II

Dynamic ProgrammingMath

Acceptance: 56.2%

#3826Hard

Minimum Partition Score

ArrayDivide and ConquerDynamic Programming+3

Acceptance: 32.6%

#3748Hard

Count Stable Subarrays

ArrayBinary SearchPrefix Sum

Acceptance: 33.0%

#3735Hard

Lexicographically Smallest String After Reverse II

Binary SearchHash FunctionRolling Hash+2

Acceptance: 48.3%

#3791Hard

Number of Balanced Integers in a Range

Dynamic Programming

Acceptance: 36.3%

#3816Hard

Lexicographically Smallest String After Deleting Duplicate Characters

GreedyHash TableMonotonic Stack+2

Acceptance: 20.9%

#3739Hard

Count Subarrays With Majority Element II

ArrayDivide and ConquerHash Table+3

Acceptance: 65.2%

#3786Hard

Total Sum of Interaction Cost in Tree Groups

ArrayDepth-First SearchTree

Acceptance: 54.3%

1 2 315 16 17 18 19 20

Page 16 of 20

Master DSA with Step-by-Step Solutions

Each solution article on FleetCode breaks down the problem into multiple approaches, from brute force to optimal, with detailed explanations and code in Python, Java, C++ and more. Understanding why an approach works - not just copying code - is what separates candidates who clear interviews from those who don't.

How to Use These Solutions

Try the problem first: Spend at least 20 minutes before reading the solution
Read all approaches: Start from brute force to understand the problem fully, then study the optimized solution
Understand the complexity: Pay attention to time and space analysis for each approach
Code it yourself: After understanding the approach, close the solution and implement from memory
Revisit after a week: Spaced repetition helps retain problem-solving patterns