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
501. Find Mode in Binary Search Tree	Easy	59.2%	Binary Search Tree Binary Tree+2	Read
502. IPO	Hard	53.6%	Array Greedy+2	Read
503. Next Greater Element II	Medium	68.7%	Array Monotonic Stack+1	Read
504. Base 7	Easy	55.3%	Math	Read
505. The Maze II	Medium	55.0%	Array Breadth-First Search+5	Read
506. Relative Ranks	Easy	75.1%	Array Heap (Priority Queue)+1	Read
507. Perfect Number	Easy	50.0%	Math	Read
508. Most Frequent Subtree Sum	Medium	69.6%	Binary Tree Depth-First Search+2	Read
509. Fibonacci Number	Easy	74.6%	Dynamic Programming Math+2	Read
510. Inorder Successor in BST II	Medium	60.9%	Binary Search Tree Binary Tree+1	Read
511. Game Play Analysis I	Easy	75.1%	Database	Read
512. Game Play Analysis II	Easy	53.4%	Database	Read
513. Find Bottom Left Tree Value	Medium	72.2%	Binary Tree Breadth-First Search+2	Read
514. Freedom Trail	Hard	59.4%	Breadth-First Search Depth-First Search+2	Read
515. Find Largest Value in Each Tree Row	Medium	66.3%	Binary Tree Breadth-First Search+2	Read
516. Longest Palindromic Subsequence	Medium	65.8%	Dynamic Programming String	Read
517. Super Washing Machines	Hard	45.3%	Array Greedy	Read
518. Coin Change II	Medium	59.7%	Array Dynamic Programming	Read
519. Random Flip Matrix	Medium	46.9%	Hash Table Math+2	Read
520. Detect Capital	Easy	56.8%	String	Read
521. Longest Uncommon Subsequence I	Easy	62.7%	String	Read
522. Longest Uncommon Subsequence II	Medium	45.2%	Array Hash Table+3	Read
523. Continuous Subarray Sum	Medium	31.3%	Array Hash Table+2	Read
524. Longest Word in Dictionary through Deleting	Medium	52.6%	Array Sorting+2	Read
525. Contiguous Array	Medium	52.2%	Array Hash Table+1	Read
526. Beautiful Arrangement	Medium	64.9%	Array Backtracking+3	Read
527. Word Abbreviation	Hard	62.7%	Array Greedy+3	Read
528. Random Pick with Weight	Medium	49.0%	Array Binary Search+3	Read
529. Minesweeper	Medium	68.7%	Array Breadth-First Search+2	Read
530. Minimum Absolute Difference in BST	Easy	59.3%	Binary Search Tree Binary Tree+3	Read
531. Lonely Pixel I	Medium	62.3%	Array Hash Table+1	Read
532. K-diff Pairs in an Array	Medium	46.3%	Array Binary Search+3	Read
533. Lonely Pixel II	Medium	48.7%	Array Hash Table+1	Read
534. Game Play Analysis III	Medium	81.0%	Database	Read
535. Encode and Decode TinyURL	Medium	86.5%	Design Hash Function+2	Read
536. Construct Binary Tree from String	Medium	58.7%	Binary Tree Depth-First Search+3	Read
537. Complex Number Multiplication	Medium	73.3%	Math Simulation+1	Read
538. Convert BST to Greater Tree	Medium	71.5%	Binary Search Tree Binary Tree+2	Read
539. Minimum Time Difference	Medium	62.7%	Array Math+2	Read
540. Single Element in a Sorted Array	Medium	59.3%	Array Binary Search	Read
541. Reverse String II	Easy	54.1%	String Two Pointers	Read
542. 01 Matrix	Medium	54.7%	Array Breadth-First Search+2	Read
543. Diameter of Binary Tree	Easy	65.8%	Binary Tree Depth-First Search+1	Read
544. Output Contest Matches	Medium	77.3%	Recursion Simulation+1	Read
545. Boundary of Binary Tree	Medium	48.0%	Binary Tree Depth-First Search+1	Read
546. Remove Boxes	Hard	49.4%	Array Dynamic Programming+1	Read
547. Number of Provinces	Medium	70.8%	Breadth-First Search Depth-First Search+2	Read
548. Split Array with Equal Sum	Hard	50.1%	Array Hash Table+1	Read
549. Binary Tree Longest Consecutive Sequence II	Medium	50.1%	Binary Tree Depth-First Search+1	Read
550. Game Play Analysis IV	Medium	38.4%	Database	Read

#501Easy

Find Mode in Binary Search Tree

Binary Search TreeBinary TreeDepth-First Search+1

Acceptance: 59.2%

#502Hard

IPO

ArrayGreedyHeap (Priority Queue)+1

Acceptance: 53.6%

#503Medium

Next Greater Element II

ArrayMonotonic StackStack

Acceptance: 68.7%

#504Easy

Base 7

Math

Acceptance: 55.3%

#505Medium

The Maze II

ArrayBreadth-First SearchDepth-First Search+4

Acceptance: 55.0%

#506Easy

Relative Ranks

ArrayHeap (Priority Queue)Sorting

Acceptance: 75.1%

#507Easy

Perfect Number

Math

Acceptance: 50.0%

#508Medium

Most Frequent Subtree Sum

Binary TreeDepth-First SearchHash Table+1

Acceptance: 69.6%

#509Easy

Fibonacci Number

Dynamic ProgrammingMathMemoization+1

Acceptance: 74.6%

#510Medium

Inorder Successor in BST II

Binary Search TreeBinary TreeTree

Acceptance: 60.9%

#511Easy

Game Play Analysis I

Database

Acceptance: 75.1%

#512Easy

Game Play Analysis II

Database

Acceptance: 53.4%

#513Medium

Find Bottom Left Tree Value

Binary TreeBreadth-First SearchDepth-First Search+1

Acceptance: 72.2%

#514Hard

Freedom Trail

Breadth-First SearchDepth-First SearchDynamic Programming+1

Acceptance: 59.4%

#515Medium

Find Largest Value in Each Tree Row

Binary TreeBreadth-First SearchDepth-First Search+1

Acceptance: 66.3%

#516Medium

Longest Palindromic Subsequence

Dynamic ProgrammingString

Acceptance: 65.8%

#517Hard

Super Washing Machines

ArrayGreedy

Acceptance: 45.3%

#518Medium

Coin Change II

ArrayDynamic Programming

Acceptance: 59.7%

#519Medium

Random Flip Matrix

Hash TableMathRandomized+1

Acceptance: 46.9%

#520Easy

Detect Capital

String

Acceptance: 56.8%

#521Easy

Longest Uncommon Subsequence I

String

Acceptance: 62.7%

#522Medium

Longest Uncommon Subsequence II

ArrayHash TableSorting+2

Acceptance: 45.2%

#523Medium

Continuous Subarray Sum

ArrayHash TableMath+1

Acceptance: 31.3%

#524Medium

Longest Word in Dictionary through Deleting

ArraySortingString+1

Acceptance: 52.6%

#525Medium

Contiguous Array

ArrayHash TablePrefix Sum

Acceptance: 52.2%

#526Medium

Beautiful Arrangement

ArrayBacktrackingBit Manipulation+2

Acceptance: 64.9%

#527Hard

Word Abbreviation

ArrayGreedySorting+2

Acceptance: 62.7%

#528Medium

Random Pick with Weight

ArrayBinary SearchMath+2

Acceptance: 49.0%

#529Medium

Minesweeper

ArrayBreadth-First SearchDepth-First Search+1

Acceptance: 68.7%

#530Easy

Minimum Absolute Difference in BST

Binary Search TreeBinary TreeBreadth-First Search+2

Acceptance: 59.3%

#531Medium

Lonely Pixel I

ArrayHash TableMatrix

Acceptance: 62.3%

#532Medium

K-diff Pairs in an Array

ArrayBinary SearchHash Table+2

Acceptance: 46.3%

#533Medium

Lonely Pixel II

ArrayHash TableMatrix

Acceptance: 48.7%

#534Medium

Game Play Analysis III

Database

Acceptance: 81.0%

#535Medium

Encode and Decode TinyURL

DesignHash FunctionHash Table+1

Acceptance: 86.5%

#536Medium

Construct Binary Tree from String

Binary TreeDepth-First SearchStack+2

Acceptance: 58.7%

#537Medium

Complex Number Multiplication

MathSimulationString

Acceptance: 73.3%

#538Medium

Convert BST to Greater Tree

Binary Search TreeBinary TreeDepth-First Search+1

Acceptance: 71.5%

#539Medium

Minimum Time Difference

ArrayMathSorting+1

Acceptance: 62.7%

#540Medium

Single Element in a Sorted Array

ArrayBinary Search

Acceptance: 59.3%

#541Easy

Reverse String II

StringTwo Pointers

Acceptance: 54.1%

#542Medium

01 Matrix

ArrayBreadth-First SearchDynamic Programming+1

Acceptance: 54.7%

#543Easy

Diameter of Binary Tree

Binary TreeDepth-First SearchTree

Acceptance: 65.8%

#544Medium

Output Contest Matches

RecursionSimulationString

Acceptance: 77.3%

#545Medium

Boundary of Binary Tree

Binary TreeDepth-First SearchTree

Acceptance: 48.0%

#546Hard

Remove Boxes

ArrayDynamic ProgrammingMemoization

Acceptance: 49.4%

#547Medium

Number of Provinces

Breadth-First SearchDepth-First SearchGraph+1

Acceptance: 70.8%

#548Hard

Split Array with Equal Sum

ArrayHash TablePrefix Sum

Acceptance: 50.1%

#549Medium

Binary Tree Longest Consecutive Sequence II

Binary TreeDepth-First SearchTree

Acceptance: 50.1%

#550Medium

Game Play Analysis IV

Database

Acceptance: 38.4%

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Master DSA with Step-by-Step Solutions

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Code it yourself: After understanding the approach, close the solution and implement from memory
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