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
415. Add Strings	Easy	52.1%	Math Simulation+1	Read
422. Valid Word Square	Easy	42.9%	Array Matrix	Read
434. Number of Segments in a String	Easy	37.6%	String	Read
441. Arranging Coins	Easy	48.1%	Binary Search Math	Read
448. Find All Numbers Disappeared in an Array	Easy	64.4%	Array Hash Table	Read
455. Assign Cookies	Easy	55.4%	Array Greedy+2	Read
459. Repeated Substring Pattern	Easy	48.6%	String String Matching	Read
461. Hamming Distance	Easy	76.7%	Bit Manipulation	Read
463. Island Perimeter	Easy	74.3%	Array Breadth-First Search+2	Read
476. Number Complement	Easy	70.3%	Bit Manipulation	Read
482. License Key Formatting	Easy	46.4%	String	Read
485. Max Consecutive Ones	Easy	66.0%	Array	Read
492. Construct the Rectangle	Easy	64.6%	Math	Read
495. Teemo Attacking	Easy	57.6%	Array Simulation	Read
496. Next Greater Element I	Easy	76.5%	Array Hash Table+2	Read
500. Keyboard Row	Easy	74.3%	Array Hash Table+1	Read
501. Find Mode in Binary Search Tree	Easy	59.2%	Binary Search Tree Binary Tree+2	Read
504. Base 7	Easy	55.3%	Math	Read
506. Relative Ranks	Easy	75.1%	Array Heap (Priority Queue)+1	Read
507. Perfect Number	Easy	50.0%	Math	Read
509. Fibonacci Number	Easy	74.6%	Dynamic Programming Math+2	Read
511. Game Play Analysis I	Easy	75.1%	Database	Read
512. Game Play Analysis II	Easy	53.4%	Database	Read
520. Detect Capital	Easy	56.8%	String	Read
521. Longest Uncommon Subsequence I	Easy	62.7%	String	Read
530. Minimum Absolute Difference in BST	Easy	59.3%	Binary Search Tree Binary Tree+3	Read
541. Reverse String II	Easy	54.1%	String Two Pointers	Read
543. Diameter of Binary Tree	Easy	65.8%	Binary Tree Depth-First Search+1	Read
551. Student Attendance Record I	Easy	50.1%	String	Read
557. Reverse Words in a String III	Easy	84.0%	String Two Pointers	Read
559. Maximum Depth of N-ary Tree	Easy	73.5%	Breadth-First Search Depth-First Search+1	Read
561. Array Partition	Easy	82.2%	Array Counting Sort+2	Read
563. Binary Tree Tilt	Easy	66.2%	Binary Tree Depth-First Search+1	Read
566. Reshape the Matrix	Easy	65.4%	Array Matrix+1	Read
572. Subtree of Another Tree	Easy	52.0%	Binary Tree Depth-First Search+3	Read
575. Distribute Candies	Easy	71.5%	Array Hash Table	Read
577. Employee Bonus	Easy	76.7%	Database	Read
584. Find Customer Referee	Easy	71.2%	Database	Read
586. Customer Placing the Largest Number of Orders	Easy	64.6%	Database	Read
589. N-ary Tree Preorder Traversal	Easy	76.7%	Depth-First Search Stack+1	Read
590. N-ary Tree Postorder Traversal	Easy	81.0%	Depth-First Search Stack+1	Read
594. Longest Harmonious Subsequence	Easy	65.1%	Array Counting+3	Read
595. Big Countries	Easy	68.2%	Database	Read
596. Classes More Than 5 Students	Easy	58.4%	Database	Read
597. Friend Requests I: Overall Acceptance Rate	Easy	41.6%	Database	Read
598. Range Addition II	Easy	59.1%	Array Math	Read
599. Minimum Index Sum of Two Lists	Easy	60.2%	Array Hash Table+1	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

#415Easy

Add Strings

MathSimulationString

Acceptance: 52.1%

#422Easy

Valid Word Square

ArrayMatrix

Acceptance: 42.9%

#434Easy

Number of Segments in a String

String

Acceptance: 37.6%

#441Easy

Arranging Coins

Binary SearchMath

Acceptance: 48.1%

#448Easy

Find All Numbers Disappeared in an Array

ArrayHash Table

Acceptance: 64.4%

#455Easy

Assign Cookies

ArrayGreedySorting+1

Acceptance: 55.4%

#459Easy

Repeated Substring Pattern

StringString Matching

Acceptance: 48.6%

#461Easy

Hamming Distance

Bit Manipulation

Acceptance: 76.7%

#463Easy

Island Perimeter

ArrayBreadth-First SearchDepth-First Search+1

Acceptance: 74.3%

#476Easy

Number Complement

Bit Manipulation

Acceptance: 70.3%

#482Easy

License Key Formatting

String

Acceptance: 46.4%

#485Easy

Max Consecutive Ones

Array

Acceptance: 66.0%

#492Easy

Construct the Rectangle

Math

Acceptance: 64.6%

#495Easy

Teemo Attacking

ArraySimulation

Acceptance: 57.6%

#496Easy

Next Greater Element I

ArrayHash TableMonotonic Stack+1

Acceptance: 76.5%

#500Easy

Keyboard Row

ArrayHash TableString

Acceptance: 74.3%

#501Easy

Find Mode in Binary Search Tree

Binary Search TreeBinary TreeDepth-First Search+1

Acceptance: 59.2%

#504Easy

Base 7

Math

Acceptance: 55.3%

#506Easy

Relative Ranks

ArrayHeap (Priority Queue)Sorting

Acceptance: 75.1%

#507Easy

Perfect Number

Math

Acceptance: 50.0%

#509Easy

Fibonacci Number

Dynamic ProgrammingMathMemoization+1

Acceptance: 74.6%

#511Easy

Game Play Analysis I

Database

Acceptance: 75.1%

#512Easy

Game Play Analysis II

Database

Acceptance: 53.4%

#520Easy

Detect Capital

String

Acceptance: 56.8%

#521Easy

Longest Uncommon Subsequence I

String

Acceptance: 62.7%

#530Easy

Minimum Absolute Difference in BST

Binary Search TreeBinary TreeBreadth-First Search+2

Acceptance: 59.3%

#541Easy

Reverse String II

StringTwo Pointers

Acceptance: 54.1%

#543Easy

Diameter of Binary Tree

Binary TreeDepth-First SearchTree

Acceptance: 65.8%

#551Easy

Student Attendance Record I

String

Acceptance: 50.1%

#557Easy

Reverse Words in a String III

StringTwo Pointers

Acceptance: 84.0%

#559Easy

Maximum Depth of N-ary Tree

Breadth-First SearchDepth-First SearchTree

Acceptance: 73.5%

#561Easy

Array Partition

ArrayCounting SortGreedy+1

Acceptance: 82.2%

#563Easy

Binary Tree Tilt

Binary TreeDepth-First SearchTree

Acceptance: 66.2%

#566Easy

Reshape the Matrix

ArrayMatrixSimulation

Acceptance: 65.4%

#572Easy

Subtree of Another Tree

Binary TreeDepth-First SearchHash Function+2

Acceptance: 52.0%

#575Easy

Distribute Candies

ArrayHash Table

Acceptance: 71.5%

#577Easy

Employee Bonus

Database

Acceptance: 76.7%

#584Easy

Find Customer Referee

Database

Acceptance: 71.2%

#586Easy

Customer Placing the Largest Number of Orders

Database

Acceptance: 64.6%

#589Easy

N-ary Tree Preorder Traversal

Depth-First SearchStackTree

Acceptance: 76.7%

#590Easy

N-ary Tree Postorder Traversal

Depth-First SearchStackTree

Acceptance: 81.0%

#594Easy

Longest Harmonious Subsequence

ArrayCountingHash Table+2

Acceptance: 65.1%

#595Easy

Big Countries

Database

Acceptance: 68.2%

#596Easy

Classes More Than 5 Students

Database

Acceptance: 58.4%

#597Easy

Friend Requests I: Overall Acceptance Rate

Database

Acceptance: 41.6%

#598Easy

Range Addition II

ArrayMath

Acceptance: 59.1%

#599Easy

Minimum Index Sum of Two Lists

ArrayHash TableString

Acceptance: 60.2%

#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%

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Master DSA with Step-by-Step Solutions

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How to Use These Solutions

Try the problem first: Spend at least 20 minutes before reading the solution
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Code it yourself: After understanding the approach, close the solution and implement from memory
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