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
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
433. Minimum Genetic Mutation	Medium	57.1%	Breadth-First Search Hash Table+1	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
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
447. Number of Boomerangs	Medium	58.0%	Array Hash Table+1	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
451. Sort Characters By Frequency	Medium	75.8%	Bucket Sort Counting+4	Read
452. Minimum Number of Arrows to Burst Balloons	Medium	61.9%	Array Greedy+1	Read
453. Minimum Moves to Equal Array Elements	Medium	58.6%	Array Math	Read
454. 4Sum II	Medium	57.9%	Array Hash Table	Read
456. 132 Pattern	Medium	34.6%	Array Binary Search+3	Read
457. Circular Array Loop	Medium	38.3%	Array Hash Table+1	Read
462. Minimum Moves to Equal Array Elements II	Medium	62.2%	Array Math+1	Read
464. Can I Win	Medium	31.7%	Bit Manipulation Bitmask+4	Read
467. Unique Substrings in Wraparound String	Medium	44.0%	Dynamic Programming String	Read
468. Validate IP Address	Medium	28.2%	String	Read
469. Convex Polygon	Medium	40.3%	Array Geometry+1	Read
470. Implement Rand10() Using Rand7()	Medium	46.4%	Math Probability and Statistics+2	Read
473. Matchsticks to Square	Medium	42.3%	Array Backtracking+3	Read
474. Ones and Zeroes	Medium	53.7%	Array Dynamic Programming+1	Read
475. Heaters	Medium	42.3%	Array Binary Search+2	Read
477. Total Hamming Distance	Medium	55.3%	Array Bit Manipulation+1	Read
478. Generate Random Point in a Circle	Medium	43.8%	Geometry Math+2	Read
481. Magical String	Medium	56.0%	String Two Pointers	Read
484. Find Permutation	Medium	67.0%	Array Greedy+2	Read
486. Predict the Winner	Medium	59.7%	Array Dynamic Programming+3	Read
487. Max Consecutive Ones II	Medium	52.0%	Array Dynamic Programming+1	Read
490. The Maze	Medium	60.4%	Array Breadth-First Search+2	Read
491. Non-decreasing Subsequences	Medium	63.1%	Array Backtracking+2	Read
494. Target Sum	Medium	52.6%	Array Backtracking+1	Read
497. Random Point in Non-overlapping Rectangles	Medium	40.2%	Array Binary Search+5	Read
498. Diagonal Traverse	Medium	67.1%	Array Matrix+1	Read
503. Next Greater Element II	Medium	68.7%	Array Monotonic Stack+1	Read
505. The Maze II	Medium	55.0%	Array Breadth-First Search+5	Read
508. Most Frequent Subtree Sum	Medium	69.6%	Binary Tree Depth-First Search+2	Read
510. Inorder Successor in BST II	Medium	60.9%	Binary Search Tree Binary Tree+1	Read
513. Find Bottom Left Tree Value	Medium	72.2%	Binary Tree Breadth-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
518. Coin Change II	Medium	59.7%	Array Dynamic Programming	Read
519. Random Flip Matrix	Medium	46.9%	Hash Table Math+2	Read

#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%

#433Medium

Minimum Genetic Mutation

Breadth-First SearchHash TableString

Acceptance: 57.1%

#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%

#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%

#447Medium

Number of Boomerangs

ArrayHash TableMath

Acceptance: 58.0%

#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%

#451Medium

Sort Characters By Frequency

Bucket SortCountingHash Table+3

Acceptance: 75.8%

#452Medium

Minimum Number of Arrows to Burst Balloons

ArrayGreedySorting

Acceptance: 61.9%

#453Medium

Minimum Moves to Equal Array Elements

ArrayMath

Acceptance: 58.6%

#454Medium

4Sum II

ArrayHash Table

Acceptance: 57.9%

#456Medium

132 Pattern

ArrayBinary SearchMonotonic Stack+2

Acceptance: 34.6%

#457Medium

Circular Array Loop

ArrayHash TableTwo Pointers

Acceptance: 38.3%

#462Medium

Minimum Moves to Equal Array Elements II

ArrayMathSorting

Acceptance: 62.2%

#464Medium

Can I Win

Bit ManipulationBitmaskDynamic Programming+3

Acceptance: 31.7%

#467Medium

Unique Substrings in Wraparound String

Dynamic ProgrammingString

Acceptance: 44.0%

#468Medium

Validate IP Address

String

Acceptance: 28.2%

#469Medium

Convex Polygon

ArrayGeometryMath

Acceptance: 40.3%

#470Medium

Implement Rand10() Using Rand7()

MathProbability and StatisticsRandomized+1

Acceptance: 46.4%

#473Medium

Matchsticks to Square

ArrayBacktrackingBit Manipulation+2

Acceptance: 42.3%

#474Medium

Ones and Zeroes

ArrayDynamic ProgrammingString

Acceptance: 53.7%

#475Medium

Heaters

ArrayBinary SearchSorting+1

Acceptance: 42.3%

#477Medium

Total Hamming Distance

ArrayBit ManipulationMath

Acceptance: 55.3%

#478Medium

Generate Random Point in a Circle

GeometryMathRandomized+1

Acceptance: 43.8%

#481Medium

Magical String

StringTwo Pointers

Acceptance: 56.0%

#484Medium

Find Permutation

ArrayGreedyStack+1

Acceptance: 67.0%

#486Medium

Predict the Winner

ArrayDynamic ProgrammingGame Theory+2

Acceptance: 59.7%

#487Medium

Max Consecutive Ones II

ArrayDynamic ProgrammingSliding Window

Acceptance: 52.0%

#490Medium

The Maze

ArrayBreadth-First SearchDepth-First Search+1

Acceptance: 60.4%

#491Medium

Non-decreasing Subsequences

ArrayBacktrackingBit Manipulation+1

Acceptance: 63.1%

#494Medium

Target Sum

ArrayBacktrackingDynamic Programming

Acceptance: 52.6%

#497Medium

Random Point in Non-overlapping Rectangles

ArrayBinary SearchMath+4

Acceptance: 40.2%

#498Medium

Diagonal Traverse

ArrayMatrixSimulation

Acceptance: 67.1%

#503Medium

Next Greater Element II

ArrayMonotonic StackStack

Acceptance: 68.7%

#505Medium

The Maze II

ArrayBreadth-First SearchDepth-First Search+4

Acceptance: 55.0%

#508Medium

Most Frequent Subtree Sum

Binary TreeDepth-First SearchHash Table+1

Acceptance: 69.6%

#510Medium

Inorder Successor in BST II

Binary Search TreeBinary TreeTree

Acceptance: 60.9%

#513Medium

Find Bottom Left Tree Value

Binary TreeBreadth-First SearchDepth-First Search+1

Acceptance: 72.2%

#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%

#518Medium

Coin Change II

ArrayDynamic Programming

Acceptance: 59.7%

#519Medium

Random Flip Matrix

Hash TableMathRandomized+1

Acceptance: 46.9%

1 2 35 6 741 42 43

Page 6 of 43

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