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
601. Human Traffic of Stadium	Hard	49.1%	Database	Read
602. Friend Requests II: Who Has the Most Friends	Medium	59.2%	Database	Read
603. Consecutive Available Seats	Easy	65.7%	Database	Read
604. Design Compressed String Iterator	Easy	40.5%	Array Design+2	Read
605. Can Place Flowers	Easy	28.8%	Array Greedy	Read
606. Construct String from Binary Tree	Medium	70.6%	Binary Tree Depth-First Search+2	Read
607. Sales Person	Easy	65.7%	Database	Read
608. Tree Node	Medium	73.1%	Database	Read
609. Find Duplicate File in System	Medium	67.6%	Array Hash Table+1	Read
610. Triangle Judgement	Easy	72.9%	Database	Read
611. Valid Triangle Number	Medium	56.8%	Array Binary Search+3	Read
612. Shortest Distance in a Plane	Medium	61.3%	Database	Read
613. Shortest Distance in a Line	Easy	80.0%	Database	Read
614. Second Degree Follower	Medium	39.3%	Database	Read
615. Average Salary: Departments VS Company	Hard	56.2%	Database	Read
616. Add Bold Tag in String	Medium	51.4%	Array Hash Table+3	Read
617. Merge Two Binary Trees	Easy	79.2%	Binary Tree Breadth-First Search+2	Read
618. Students Report By Geography	Hard	63.5%	Database	Read
619. Biggest Single Number	Easy	67.3%	Database	Read
620. Not Boring Movies	Easy	74.5%	Database	Read
621. Task Scheduler	Medium	63.4%	Array Counting+4	Read
622. Design Circular Queue	Medium	55.4%	Array Design+2	Read
623. Add One Row to Tree	Medium	64.1%	Binary Tree Breadth-First Search+2	Read
624. Maximum Distance in Arrays	Medium	45.7%	Array Greedy	Read
625. Minimum Factorization	Medium	34.2%	Greedy Math	Read
626. Exchange Seats	Medium	71.6%	Database	Read
627. Swap Salary	Easy	83.6%	Database	Read
628. Maximum Product of Three Numbers	Easy	48.0%	Array Math+1	Read
629. K Inverse Pairs Array	Hard	49.2%	Dynamic Programming	Read
630. Course Schedule III	Hard	42.1%	Array Greedy+2	Read
631. Design Excel Sum Formula	Hard	39.9%	Array Design+3	Read
632. Smallest Range Covering Elements from K Lists	Hard	70.3%	Array Greedy+4	Read
633. Sum of Square Numbers	Medium	37.0%	Binary Search Math+1	Read
634. Find the Derangement of An Array	Medium	41.9%	Dynamic Programming Math	Read
635. Design Log Storage System	Medium	59.8%	Design Hash Table+2	Read
636. Exclusive Time of Functions	Medium	66.2%	Array Stack	Read
637. Average of Levels in Binary Tree	Easy	74.8%	Binary Tree Breadth-First Search+2	Read
638. Shopping Offers	Medium	52.3%	Array Backtracking+4	Read
639. Decode Ways II	Hard	31.8%	Dynamic Programming String	Read
640. Solve the Equation	Medium	46.7%	Math Simulation+1	Read
641. Design Circular Deque	Medium	64.6%	Array Design+2	Read
642. Design Search Autocomplete System	Hard	49.9%	Data Stream Depth-First Search+5	Read
643. Maximum Average Subarray I	Easy	49.2%	Array Sliding Window	Read
644. Maximum Average Subarray II	Hard	37.7%	Array Binary Search+1	Read
645. Set Mismatch	Easy	43.4%	Array Bit Manipulation+2	Read
646. Maximum Length of Pair Chain	Medium	62.2%	Array Dynamic Programming+2	Read
647. Palindromic Substrings	Medium	73.2%	Dynamic Programming String+1	Read
648. Replace Words	Medium	68.7%	Array Hash Table+2	Read
649. Dota2 Senate	Medium	50.3%	Greedy Queue+1	Read
650. 2 Keys Keyboard	Medium	59.6%	Dynamic Programming Math	Read

#601Hard

Human Traffic of Stadium

Database

Acceptance: 49.1%

#602Medium

Friend Requests II: Who Has the Most Friends

Database

Acceptance: 59.2%

#603Easy

Consecutive Available Seats

Database

Acceptance: 65.7%

#604Easy

Design Compressed String Iterator

ArrayDesignIterator+1

Acceptance: 40.5%

#605Easy

Can Place Flowers

ArrayGreedy

Acceptance: 28.8%

#606Medium

Construct String from Binary Tree

Binary TreeDepth-First SearchString+1

Acceptance: 70.6%

#607Easy

Sales Person

Database

Acceptance: 65.7%

#608Medium

Tree Node

Database

Acceptance: 73.1%

#609Medium

Find Duplicate File in System

ArrayHash TableString

Acceptance: 67.6%

#610Easy

Triangle Judgement

Database

Acceptance: 72.9%

#611Medium

Valid Triangle Number

ArrayBinary SearchGreedy+2

Acceptance: 56.8%

#612Medium

Shortest Distance in a Plane

Database

Acceptance: 61.3%

#613Easy

Shortest Distance in a Line

Database

Acceptance: 80.0%

#614Medium

Second Degree Follower

Database

Acceptance: 39.3%

#615Hard

Average Salary: Departments VS Company

Database

Acceptance: 56.2%

#616Medium

Add Bold Tag in String

ArrayHash TableString+2

Acceptance: 51.4%

#617Easy

Merge Two Binary Trees

Binary TreeBreadth-First SearchDepth-First Search+1

Acceptance: 79.2%

#618Hard

Students Report By Geography

Database

Acceptance: 63.5%

#619Easy

Biggest Single Number

Database

Acceptance: 67.3%

#620Easy

Not Boring Movies

Database

Acceptance: 74.5%

#621Medium

Task Scheduler

ArrayCountingGreedy+3

Acceptance: 63.4%

#622Medium

Design Circular Queue

ArrayDesignLinked List+1

Acceptance: 55.4%

#623Medium

Add One Row to Tree

Binary TreeBreadth-First SearchDepth-First Search+1

Acceptance: 64.1%

#624Medium

Maximum Distance in Arrays

ArrayGreedy

Acceptance: 45.7%

#625Medium

Minimum Factorization

GreedyMath

Acceptance: 34.2%

#626Medium

Exchange Seats

Database

Acceptance: 71.6%

#627Easy

Swap Salary

Database

Acceptance: 83.6%

#628Easy

Maximum Product of Three Numbers

ArrayMathSorting

Acceptance: 48.0%

#629Hard

K Inverse Pairs Array

Dynamic Programming

Acceptance: 49.2%

#630Hard

Course Schedule III

ArrayGreedyHeap (Priority Queue)+1

Acceptance: 42.1%

#631Hard

Design Excel Sum Formula

ArrayDesignGraph+2

Acceptance: 39.9%

#632Hard

Smallest Range Covering Elements from K Lists

ArrayGreedyHash Table+3

Acceptance: 70.3%

#633Medium

Sum of Square Numbers

Binary SearchMathTwo Pointers

Acceptance: 37.0%

#634Medium

Find the Derangement of An Array

Dynamic ProgrammingMath

Acceptance: 41.9%

#635Medium

Design Log Storage System

DesignHash TableOrdered Set+1

Acceptance: 59.8%

#636Medium

Exclusive Time of Functions

ArrayStack

Acceptance: 66.2%

#637Easy

Average of Levels in Binary Tree

Binary TreeBreadth-First SearchDepth-First Search+1

Acceptance: 74.8%

#638Medium

Shopping Offers

ArrayBacktrackingBit Manipulation+3

Acceptance: 52.3%

#639Hard

Decode Ways II

Dynamic ProgrammingString

Acceptance: 31.8%

#640Medium

Solve the Equation

MathSimulationString

Acceptance: 46.7%

#641Medium

Design Circular Deque

ArrayDesignLinked List+1

Acceptance: 64.6%

#642Hard

Design Search Autocomplete System

Data StreamDepth-First SearchDesign+4

Acceptance: 49.9%

#643Easy

Maximum Average Subarray I

ArraySliding Window

Acceptance: 49.2%

#644Hard

Maximum Average Subarray II

ArrayBinary SearchPrefix Sum

Acceptance: 37.7%

#645Easy

Set Mismatch

ArrayBit ManipulationHash Table+1

Acceptance: 43.4%

#646Medium

Maximum Length of Pair Chain

ArrayDynamic ProgrammingGreedy+1

Acceptance: 62.2%

#647Medium

Palindromic Substrings

Dynamic ProgrammingStringTwo Pointers

Acceptance: 73.2%

#648Medium

Replace Words

ArrayHash TableString+1

Acceptance: 68.7%

#649Medium

Dota2 Senate

GreedyQueueString

Acceptance: 50.3%

#650Medium

2 Keys Keyboard

Dynamic ProgrammingMath

Acceptance: 59.6%

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Master DSA with Step-by-Step Solutions

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