Math
163 problems · 107 with full explanations
33 Easy59 Medium10 Hard
Math problems test number theory, combinatorics, and modular arithmetic. Common tools: GCD/LCM (Euclidean algorithm), prime sieve, modular inverse (Fermat's little theorem), digit manipulation, and bit tricks. Overflow is a key concern in C# — use long when products may exceed 2³¹.
How to practice
To practice Math problems effectively, start with the Easy problems listed below, trace through each solution on paper, then re-implement without looking. When you can recognise the math pattern within 30 seconds of reading a new problem, move on to Medium difficulty. Use the related topic pages and our study guide for a structured progression.
Start here (Easy + explained)
All Math problems
- 12.Integer to RomanMedium
- 13.Roman to IntegerEasy
- 29.Divide Two IntegersMedium
- 66.Plus OneEasy
- 67.Add BinaryEasy
- 70.Climbing StairsEasy
- 166.Fraction to Recurring DecimalMedium
- 171.Excel Sheet Column NumberEasy
- 172.Factorial Trailing ZeroesMedium
- 179.Largest NumberMedium
- 189.Rotate ArrayMedium
- 202.Happy NumberEasy
- 231.Power of TwoEasy
- 241.Different Ways to Add ParenthesesMedium
- 263.Ugly NumberEasy
- 264.Ugly Number IIMedium
- 273.Integer to English WordsHard
- 319.Bulb SwitcherMedium
- 326.Power of ThreeEasy
- 342.Power of FourEasy
- 367.Valid Perfect SquareUnknown
- 368.Largest Divisible SubsetMedium
- 400.Nth DigitMedium
- 405.Convert a Number to HexadecimalEasy
- 477.Total Hamming DistanceMedium
- 479.Largest Palindrome ProductUnknown
- 539.Minimum Time DifferenceMedium
- 564.Find the Closest PalindromeHard
- 592.Fraction Addition and SubtractionUnknown
- 593.Valid SquareMedium
- 633.Sum of Square NumbersMedium
- 650.2 Keys KeyboardMedium
- 670.Maximum SwapMedium
- 679.24 GameHard
- 726.Number of AtomsHard
- 762.Prime Number of Set Bits in Binary RepresentationMedium
- 781.Rabbits in ForestMedium
- 788.Rotated DigitsMedium
- 808.Soup ServingsUnknown
- 812.Largest Triangle AreaHard
- 822.Card Flipping GameUnknown
- 829.Consecutive Numbers SumHard
- 837.New 21 GameMedium
- 840.Magic Squares In GridMedium
- 856.Score of ParenthesesMedium
- 857.Minimum Cost to Hire K WorkersHard
- 866.Prime PalindromeMedium
- 869.Reordered Power of 2Medium
- 878.Nth Magical NumberHard
- 885.Spiral Matrix IIIMedium
- 892.Surface Area of 3D ShapesMedium
- 898.Bitwise ORs of SubarraysMedium
- 902.Numbers At Most N Given Digit SetHard
- 908.Smallest Range IEasy
- 961.N-Repeated Element in Size 2N ArrayUnknown
- 973.K Closest Points to OriginMedium
- 976.Largest Perimeter TriangleMedium
- 1006.Clumsy FactorialMedium
- 1009.Complement of Base 10 IntegerEasy
- 1015.Smallest Integer Divisible by KMedium
- 1018.Binary Prefix Divisible By 5Easy
- 1039.Minimum Score Triangulation of PolygonMedium
- 1140.Stone Game IIMedium
- 1248.Count Number of Nice SubarraysMedium
- 1266.Minimum Time Visiting All PointsEasy
- 1290.Convert Binary Number in a Linked List to IntegerEasy
- 1304.Find N Unique Integers Sum up to ZeroUnknown
- 1317.Convert Integer to the Sum of Two No-Zero IntegersUnknown
- 1323.Maximum 69 NumberEasy
- 1352.Product of the Last K NumbersMedium
- 1390.Four DivisorsUnknown
- 1395.Count Number of TeamsUnknown
- 1399.Count Largest GroupUnknown
- 1432.Max Difference You Can Get From Changing an IntegerUnknown
- 1486.XOR Operation in an ArrayEasy
- 1513.Number of Substrings With Only 1sUnknown
- 1518.Water BottlesUnknown
- 1523.Count Odd Numbers in an Interval RangeEasy
- 1524.Number of Sub-arrays With Odd SumMedium
- 1573.Number of Ways to Split a StringUnknown
- 1621.Number of Sets of K Non-Overlapping Line SegmentsUnknown
- 1622.Fancy SequenceUnknown
- 1680.Concatenation of Consecutive Binary NumbersUnknown
- 1701.Average Waiting TimeMedium
- 1716.Calculate Money in Leetcode BankEasy
- 1766.Tree of CoprimesUnknown
- 1780.Check if Number is a Sum of Powers of ThreeUnknown
- 1799.Maximize Score After N OperationsUnknown
- 1823.Find the Winner of the Circular GameMedium
- 1862.Sum of Floored PairsUnknown
- 1863.Sum of All Subset XOR TotalsUnknown
- 1895.Largest Magic SquareUnknown
- 1922.Count Good NumbersUnknown
- 1925.Count Square Sum TriplesUnknown
- 1994.The Number of Good SubsetsUnknown
- 2028.Find Missing ObservationsUnknown
- 2033.Minimum Operations to Make a Uni-Value GridUnknown
- 2048.Next Greater Numerically Balanced NumberMedium
- 2081.Sum of k-Mirror NumbersUnknown
- 2094.Finding 3-Digit Even NumbersUnknown
- 2125.Number of Laser Beams in a BankMedium
- 2147.Number of Ways to Divide a Long CorridorUnknown
- 2169.Count Operations to Obtain ZeroUnknown
- 2197.Replace Non-Coprime Numbers in ArrayUnknown
- 2221.Find Triangular Sum of an ArrayMedium
- 2338.Count the Number of Ideal ArraysMedium
- 2344.Minimum Deletions to Make Array DivisibleHard
- 2348.Number of Zero-Filled SubarraysMedium
- 2400.Number of Ways to Reach a Position After Exactly k StepsMedium
- 2409.Count Days Spent TogetherEasy
- 2509.Cycle Length Queries in a TreeMedium
- 2523.Closest Prime Numbers in RangeMedium
- 2566.Maximum Difference by Remapping a DigitEasy
- 2572.Count the Number of Square-Free SubsetsUnknown
- 2579.Count Total Number of Colored CellsMedium
- 2654.Minimum Number of Operations to Make All Array Elements Equal to 1Unknown
- 2698.Find the Punishment Number of an IntegerUnknown
- 2787.Ways to Express an Integer as Sum of PowersUnknown
- 2807.Insert Greatest Common Divisors in Linked ListMedium
- 2818.Apply Operations to Maximize ScoreUnknown
- 2843.Count Symmetric IntegersMedium
- 2845.Count of Interesting SubarraysMedium
- 2894.Divisible and Non-divisible Sums DifferenceEasy
- 2906.Construct Product MatrixEasy
- 2929.Distribute Candies Among Children IIMedium
- 2930.Number of Strings Which Can Be Rearranged to Contain SubstringMedium
- 2943.Maximize Area of Square Hole in GridMedium
- 2975.Maximum Square Area by Removing Fences From a FieldUnknown
- 2999.Count the Number of Powerful IntegersUnknown
- 3000.Maximum Area of Longest Diagonal RectangleMedium
- 3021.Alice and Bob Playing Flower GameUnknown
- 3024.Type of TriangleEasy
- 3025.Find the Number of Ways to Place People IUnknown
- 3027.Find the Number of Ways to Place People IIUnknown
- 3047.Find the Largest Area of Square Inside Two RectanglesEasy
- 3100.Water Bottles IIEasy
- 3116.Kth Smallest Amount With Single Denomination CombinationMedium
- 3190.Find Minimum Operations to Make All Elements Divisible by ThreeEasy
- 3227.Vowels Game in a StringUnknown
- 3264.Final Array State After K Multiplication Operations IEasy
- 3272.Find the Count of Good IntegersUnknown
- 3289.The Two Sneaky Numbers of DigitvilleMedium
- 3296.Minimum Number of Seconds to Make Mountain Height ZeroMedium
- 3304.Find the K-th Character in String Game IUnknown
- 3307.Find the K-th Character in String Game IIUnknown
- 3335.Total Characters in String After Transformations IMedium
- 3337.Total Characters in String After Transformations IIUnknown
- 3343.Count Number of Balanced PermutationsUnknown
- 3370.Smallest Number With All Set BitsEasy
- 3405.Count the Number of Arrays with K Matching Adjacent ElementsUnknown
- 3432.Count Partitions with Even Sum DifferenceEasy
- 3443.Maximum Manhattan Distance After K ChangesUnknown
- 3453.Separate Squares IUnknown
- 3454.Separate Squares IIUnknown
- 3461.Check If Digits Are Equal in String After Operations IEasy
- 3494.Find the Minimum Amount of Time to Brew PotionsUnknown
- 3495.Minimum Operations to Make Array Elements ZeroEasy
- 3512.Minimum Operations to Make Array Sum Divisible by KUnknown
- 3539.Find Sum of Array Product of Magical SequencesUnknown
- 3577.Count the Number of Computer Unlocking PermutationsUnknown
- 3583.Count Special TripletsUnknown
- 3623.Count Number of Trapezoids IUnknown
- 3625.Count Number of Trapezoids IIUnknown