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Solutions, explained

Every approach from brute force to the best one, with code in Python, Java, C++ and more.

Array504 Dynamic Programming294 String177 Math157 Binary Search121 Hash Table119 Sorting101 Greedy94 Bit Manipulation85 Graph84 Depth-First Search77 Heap (Priority Queue)75 All topics

Hard · 864 results

Time Taken to Cross the Door

2534.Time Taken to Cross the Door

HardArrayQueueSimulation50.1% acceptance3 companiesPremium elsewhere, free hereVideo

Difference Between Maximum and Minimum Price Sum

2538.Difference Between Maximum and Minimum Price Sum

HardArrayDepth-First SearchDynamic Programming34.5% acceptance2 companiesVideo

Check if Point Is Reachable

2543.Check if Point Is Reachable

HardMathNumber Theory45.5% acceptance1 companyVideo

Minimum Cost to Split an Array

2547.Minimum Cost to Split an Array

HardArrayCountingDynamic Programming45.4% acceptance1 companyVideo

Put Marbles in Bags

2551.Put Marbles in Bags

HardArrayGreedyHeap (Priority Queue)72.2% acceptance8 companiesVideo

Count Increasing Quadruplets

2552.Count Increasing Quadruplets

HardArrayBinary Indexed TreeDynamic Programming34.6% acceptance2 companiesVideo

Rearranging Fruits

2561.Rearranging Fruits

HardArrayGreedyHash Table57.4% acceptance9 companiesVideo

Subsequence With the Minimum Score

2565.Subsequence With the Minimum Score

HardBinary SearchStringTwo Pointers33.8% acceptance1 companyVideo

Handling Sum Queries After Update

2569.Handling Sum Queries After Update

HardArraySegment Tree32.4% acceptance1 companyVideo

Find the String with LCP

2573.Find the String with LCP

HardArrayDynamic ProgrammingGreedy63.3% acceptance1 companyVideo

Minimum Time to Visit a Cell In a Grid

2577.Minimum Time to Visit a Cell In a Grid

HardArrayBreadth-First SearchGraph56.3% acceptance4 companiesVideo

Count Number of Possible Root Nodes

2581.Count Number of Possible Root Nodes

HardArrayDepth-First SearchDynamic Programming49.3% acceptanceVideo

Split the Array to Make Coprime Products

2584.Split the Array to Make Coprime Products

HardArrayHash TableMath29.3% acceptance1 companyVideo

Number of Ways to Earn Points

2585.Number of Ways to Earn Points

HardArrayDynamic Programming60.2% acceptance1 companyVideo

Minimum Time to Complete All Tasks

2589.Minimum Time to Complete All Tasks

HardArrayBinary SearchGreedy39.6% acceptance1 companyVideo

Collect Coins in a Tree

2603.Collect Coins in a Tree

HardArrayGraphTopological Sort39.6% acceptance13 companiesVideo

Minimum Time to Eat All Grains

2604.Minimum Time to Eat All Grains

HardArrayBinary SearchSorting40.8% acceptance1 companyPremium elsewhere, free hereVideo

Shortest Cycle in a Graph

2608.Shortest Cycle in a Graph

HardBreadth-First SearchGraph40.5% acceptance4 companiesVideo

Minimum Reverse Operations

2612.Minimum Reverse Operations

HardArrayBreadth-First SearchOrdered Set17.5% acceptance1 companyVideo

Beautiful Pairs

2613.Beautiful Pairs

HardArrayDivide and ConquerGeometry46.9% acceptancePremium elsewhere, free hereVideo

Minimum Number of Visited Cells in a Grid

2617.Minimum Number of Visited Cells in a Grid

HardArrayBreadth-First SearchDynamic Programming24.1% acceptance3 companiesVideo

2630.Memoize II

Hard31.5% acceptance1 companyVideo

Design Graph With Shortest Path Calculator

2642.Design Graph With Shortest Path Calculator

HardDesignGraphHeap (Priority Queue)65.6% acceptance2 companiesVideo

Minimize the Total Price of the Trips

2646.Minimize the Total Price of the Trips

HardArrayDepth-First SearchDynamic Programming48.5% acceptanceVideo

Color the Triangle Red

2647.Color the Triangle Red

HardArrayMath58.0% acceptancePremium elsewhere, free hereVideo

Design Cancellable Function

2650.Design Cancellable Function

Hard49.6% acceptanceVideo

Make Array Empty

2659.Make Array Empty

HardArrayBinary Indexed TreeBinary Search27.4% acceptance2 companiesVideo

Lexicographically Smallest Beautiful String

2663.Lexicographically Smallest Beautiful String

HardGreedyString37.9% acceptance2 companiesVideo

Array of Objects to Matrix

2675.Array of Objects to Matrix

Hard68.4% acceptancePremium elsewhere, free hereVideo

Power of Heroes

2681.Power of Heroes

HardArrayDynamic ProgrammingMath30.6% acceptanceVideo

Modify Graph Edge Weights

2699.Modify Graph Edge Weights

HardGraphHeap (Priority Queue)Shortest Path55.6% acceptance1 companyVideo

Consecutive Transactions with Increasing Amounts

2701.Consecutive Transactions with Increasing Amounts

HardDatabase35.4% acceptancePremium elsewhere, free hereVideo

Minimum Operations to Make Numbers Non-positive

2702.Minimum Operations to Make Numbers Non-positive

HardArrayBinary Search44.1% acceptance1 companyPremium elsewhere, free hereVideo

Greatest Common Divisor Traversal

2709.Greatest Common Divisor Traversal

HardArrayMathNumber Theory41.6% acceptanceVideo

Maximum Strictly Increasing Cells in a Matrix

2713.Maximum Strictly Increasing Cells in a Matrix

HardArrayBinary SearchDynamic Programming31.3% acceptanceVideo

Find Shortest Path with K Hops

2714.Find Shortest Path with K Hops

HardGraphHeap (Priority Queue)Shortest Path68.7% acceptance1 companyPremium elsewhere, free hereVideo

Count of Integers

2719.Count of Integers

HardDynamic ProgrammingMathString38.9% acceptance2 companiesVideo

Popularity Percentage

2720.Popularity Percentage

HardDatabase53.5% acceptancePremium elsewhere, free hereVideo

Find a Good Subset of the Matrix

2732.Find a Good Subset of the Matrix

HardArrayBit ManipulationHash Table45.4% acceptanceVideo

Maximum Sum Queries

2736.Maximum Sum Queries

HardArrayBinary Indexed TreeBinary Search30.8% acceptanceVideo

Painting the Walls

2742.Painting the Walls

HardArrayDynamic Programming49.0% acceptance5 companiesVideo

Robot Collisions

2751.Robot Collisions

HardArraySimulationSorting61.6% acceptance7 companiesVideo

Customers with Maximum Number of Transactions on Consecutive Days

2752.Customers with Maximum Number of Transactions on Consecutive Days

HardDatabase42.5% acceptancePremium elsewhere, free hereVideo

Count Houses in a Circular Street II

2753.Count Houses in a Circular Street II

Hard61.5% acceptancePremium elsewhere, free hereVideo

Convert JSON String to Object

2759.Convert JSON String to Object

Hard61.7% acceptance2 companiesPremium elsewhere, free hereVideo

Sum of Imbalance Numbers of All Subarrays

2763.Sum of Imbalance Numbers of All Subarrays

HardArrayHash TableOrdered Set41.9% acceptance1 companyVideo

Length of the Longest Valid Substring

2781.Length of the Longest Valid Substring

HardArrayHash TableSliding Window38.3% acceptance3 companiesVideo

Maximum Number of Groups With Increasing Length

2790.Maximum Number of Groups With Increasing Length

HardArrayBinary SearchGreedy23.0% acceptance1 companyVideo

Count Paths That Can Form a Palindrome in a Tree

2791.Count Paths That Can Form a Palindrome in a Tree

HardBit ManipulationBitmaskDepth-First Search52.6% acceptance4 companiesVideo

Count Nodes That Are Great Enough

2792.Count Nodes That Are Great Enough

HardBinary TreeDepth-First SearchDivide and Conquer57.1% acceptancePremium elsewhere, free hereVideo

Showing 551–600 of 864

How to use these solutions

Each solution breaks the problem into approaches, usually from brute force to the best one, and explains why each works. Code comes in Python, Java, C++ and other languages. Knowing why an approach works matters more in an interview than remembering the code.

Try the problem first. Give it at least 20 minutes before you open the solution.
Read every approach. The brute force shows you the problem; the faster ones show the pattern.
Check the complexity. Note the time and space of each approach and what makes the difference.
Write it yourself. Close the solution and code it from memory in the editor.
Come back in a week. Solving it again later is what makes the pattern stick.

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