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
401. Binary Watch	Easy	65.9%	Backtracking Bit Manipulation	Read
402. Remove K Digits	Medium	37.7%	Greedy Monotonic Stack+2	Read
403. Frog Jump	Hard	47.2%	Array Dynamic Programming	Read
404. Sum of Left Leaves	Easy	63.1%	Binary Tree Breadth-First Search+2	Read
405. Convert a Number to Hexadecimal	Easy	54.8%	Bit Manipulation Math	Read
406. Queue Reconstruction by Height	Medium	74.6%	Array Binary Indexed Tree+2	Read
407. Trapping Rain Water II	Hard	64.0%	Array Breadth-First Search+2	Read
408. Valid Word Abbreviation	Easy	37.0%	String Two Pointers	Read
409. Longest Palindrome	Easy	55.9%	Greedy Hash Table+1	Read
410. Split Array Largest Sum	Hard	61.2%	Array Binary Search+3	Read
411. Minimum Unique Word Abbreviation	Hard	40.5%	Array Backtracking+2	Read
412. Fizz Buzz	Easy	75.9%	Math Simulation+1	Read
413. Arithmetic Slices	Medium	65.0%	Array Dynamic Programming+1	Read
414. Third Maximum Number	Easy	40.3%	Array Sorting	Read
415. Add Strings	Easy	52.1%	Math Simulation+1	Read
416. Partition Equal Subset Sum	Medium	49.9%	Array Dynamic Programming	Read
417. Pacific Atlantic Water Flow	Medium	61.3%	Array Breadth-First Search+2	Read
418. Sentence Screen Fitting	Medium	36.3%	Array Dynamic Programming+1	Read
419. Battleships in a Board	Medium	77.4%	Array Depth-First Search+1	Read
420. Strong Password Checker	Hard	16.1%	Greedy Heap (Priority Queue)+1	Read
421. Maximum XOR of Two Numbers in an Array	Medium	53.8%	Array Bit Manipulation+2	Read
422. Valid Word Square	Easy	42.9%	Array Matrix	Read
423. Reconstruct Original Digits from English	Medium	52.8%	Hash Table Math+1	Read
424. Longest Repeating Character Replacement	Medium	60.4%	Hash Table Sliding Window+1	Read
425. Word Squares	Hard	54.7%	Array Backtracking+2	Read
426. Convert Binary Search Tree to Sorted Doubly Linked List	Medium	65.2%	Binary Search Tree Binary Tree+5	Read
427. Construct Quad Tree	Medium	78.2%	Array Divide and Conquer+2	Read
428. Serialize and Deserialize N-ary Tree	Hard	68.7%	Breadth-First Search Depth-First Search+2	Read
429. N-ary Tree Level Order Traversal	Medium	71.6%	Breadth-First Search Tree	Read
430. Flatten a Multilevel Doubly Linked List	Medium	63.3%	Depth-First Search Doubly-Linked List+1	Read
431. Encode N-ary Tree to Binary Tree	Hard	80.6%	Binary Tree Breadth-First Search+3	Read
432. All O`one Data Structure	Hard	44.2%	Design Doubly-Linked List+2	Read
433. Minimum Genetic Mutation	Medium	57.1%	Breadth-First Search Hash Table+1	Read
434. Number of Segments in a String	Easy	37.6%	String	Read
435. Non-overlapping Intervals	Medium	57.5%	Array Dynamic Programming+2	Read
436. Find Right Interval	Medium	56.1%	Array Binary Search+1	Read
437. Path Sum III	Medium	46.6%	Binary Tree Depth-First Search+1	Read
438. Find All Anagrams in a String	Medium	54.1%	Hash Table Sliding Window+1	Read
439. Ternary Expression Parser	Medium	62.6%	Recursion Stack+1	Read
440. K-th Smallest in Lexicographical Order	Hard	46.2%	Trie	Read
441. Arranging Coins	Easy	48.1%	Binary Search Math	Read
442. Find All Duplicates in an Array	Medium	76.8%	Array Hash Table	Read
443. String Compression	Medium	60.3%	String Two Pointers	Read
444. Sequence Reconstruction	Medium	31.2%	Array Graph+1	Read
445. Add Two Numbers II	Medium	63.1%	Linked List Math+1	Read
446. Arithmetic Slices II - Subsequence	Hard	55.1%	Array Dynamic Programming	Read
447. Number of Boomerangs	Medium	58.0%	Array Hash Table+1	Read
448. Find All Numbers Disappeared in an Array	Easy	64.4%	Array Hash Table	Read
449. Serialize and Deserialize BST	Medium	59.5%	Binary Search Tree Binary Tree+5	Read
450. Delete Node in a BST	Medium	55.1%	Binary Search Tree Binary Tree+1	Read

#401Easy

Binary Watch

BacktrackingBit Manipulation

Acceptance: 65.9%

#402Medium

Remove K Digits

GreedyMonotonic StackStack+1

Acceptance: 37.7%

#403Hard

Frog Jump

ArrayDynamic Programming

Acceptance: 47.2%

#404Easy

Sum of Left Leaves

Binary TreeBreadth-First SearchDepth-First Search+1

Acceptance: 63.1%

#405Easy

Convert a Number to Hexadecimal

Bit ManipulationMath

Acceptance: 54.8%

#406Medium

Queue Reconstruction by Height

ArrayBinary Indexed TreeSegment Tree+1

Acceptance: 74.6%

#407Hard

Trapping Rain Water II

ArrayBreadth-First SearchHeap (Priority Queue)+1

Acceptance: 64.0%

#408Easy

Valid Word Abbreviation

StringTwo Pointers

Acceptance: 37.0%

#409Easy

Longest Palindrome

GreedyHash TableString

Acceptance: 55.9%

#410Hard

Split Array Largest Sum

ArrayBinary SearchDynamic Programming+2

Acceptance: 61.2%

#411Hard

Minimum Unique Word Abbreviation

ArrayBacktrackingBit Manipulation+1

Acceptance: 40.5%

#412Easy

Fizz Buzz

MathSimulationString

Acceptance: 75.9%

#413Medium

Arithmetic Slices

ArrayDynamic ProgrammingSliding Window

Acceptance: 65.0%

#414Easy

Third Maximum Number

ArraySorting

Acceptance: 40.3%

#415Easy

Add Strings

MathSimulationString

Acceptance: 52.1%

#416Medium

Partition Equal Subset Sum

ArrayDynamic Programming

Acceptance: 49.9%

#417Medium

Pacific Atlantic Water Flow

ArrayBreadth-First SearchDepth-First Search+1

Acceptance: 61.3%

#418Medium

Sentence Screen Fitting

ArrayDynamic ProgrammingString

Acceptance: 36.3%

#419Medium

Battleships in a Board

ArrayDepth-First SearchMatrix

Acceptance: 77.4%

#420Hard

Strong Password Checker

GreedyHeap (Priority Queue)String

Acceptance: 16.1%

#421Medium

Maximum XOR of Two Numbers in an Array

ArrayBit ManipulationHash Table+1

Acceptance: 53.8%

#422Easy

Valid Word Square

ArrayMatrix

Acceptance: 42.9%

#423Medium

Reconstruct Original Digits from English

Hash TableMathString

Acceptance: 52.8%

#424Medium

Longest Repeating Character Replacement

Hash TableSliding WindowString

Acceptance: 60.4%

#425Hard

Word Squares

ArrayBacktrackingString+1

Acceptance: 54.7%

#426Medium

Convert Binary Search Tree to Sorted Doubly Linked List

Binary Search TreeBinary TreeDepth-First Search+4

Acceptance: 65.2%

#427Medium

Construct Quad Tree

ArrayDivide and ConquerMatrix+1

Acceptance: 78.2%

#428Hard

Serialize and Deserialize N-ary Tree

Breadth-First SearchDepth-First SearchString+1

Acceptance: 68.7%

#429Medium

N-ary Tree Level Order Traversal

Breadth-First SearchTree

Acceptance: 71.6%

#430Medium

Flatten a Multilevel Doubly Linked List

Depth-First SearchDoubly-Linked ListLinked List

Acceptance: 63.3%

#431Hard

Encode N-ary Tree to Binary Tree

Binary TreeBreadth-First SearchDepth-First Search+2

Acceptance: 80.6%

#432Hard

All O`one Data Structure

DesignDoubly-Linked ListHash Table+1

Acceptance: 44.2%

#433Medium

Minimum Genetic Mutation

Breadth-First SearchHash TableString

Acceptance: 57.1%

#434Easy

Number of Segments in a String

String

Acceptance: 37.6%

#435Medium

Non-overlapping Intervals

ArrayDynamic ProgrammingGreedy+1

Acceptance: 57.5%

#436Medium

Find Right Interval

ArrayBinary SearchSorting

Acceptance: 56.1%

#437Medium

Path Sum III

Binary TreeDepth-First SearchTree

Acceptance: 46.6%

#438Medium

Find All Anagrams in a String

Hash TableSliding WindowString

Acceptance: 54.1%

#439Medium

Ternary Expression Parser

RecursionStackString

Acceptance: 62.6%

#440Hard

K-th Smallest in Lexicographical Order

Trie

Acceptance: 46.2%

#441Easy

Arranging Coins

Binary SearchMath

Acceptance: 48.1%

#442Medium

Find All Duplicates in an Array

ArrayHash Table

Acceptance: 76.8%

#443Medium

String Compression

StringTwo Pointers

Acceptance: 60.3%

#444Medium

Sequence Reconstruction

ArrayGraphTopological Sort

Acceptance: 31.2%

#445Medium

Add Two Numbers II

Linked ListMathStack

Acceptance: 63.1%

#446Hard

Arithmetic Slices II - Subsequence

ArrayDynamic Programming

Acceptance: 55.1%

#447Medium

Number of Boomerangs

ArrayHash TableMath

Acceptance: 58.0%

#448Easy

Find All Numbers Disappeared in an Array

ArrayHash Table

Acceptance: 64.4%

#449Medium

Serialize and Deserialize BST

Binary Search TreeBinary TreeBreadth-First Search+4

Acceptance: 59.5%

#450Medium

Delete Node in a BST

Binary Search TreeBinary TreeTree

Acceptance: 55.1%

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