Mathematics

This plan collects problems where the answer comes from a formula or a counting argument rather than a data structure: primes and GCDs, counting arrangements modulo a large prime, expected values, and deciding who wins a two-player game.

Its seven chapters are number theory, combinatorics, probability and expected value, game theory, computational geometry, randomized algorithms, and miscellaneous math. Take it when problems keep stalling on the math step rather than the code.

189 problemsRating 1145–28007 Chapters

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I. Number Theory

§1.1 Primality Testing

Problem	Rating
3115. Maximum Prime Difference	1294
2614. Prime in Diagonal	1375
762. Prime Number of Set Bits in Binary Representation	1383
3556. Sum of Largest Prime Substrings	1440
3044. Most Frequent Prime	1737
866. Prime Palindrome	1938

§1.2 Sieve of Eratosthenes

Problem	Rating
204. Count Primes	Unrated
3618. Split Array by Prime Indices	1227
3591. Check If Any Element Has Prime Frequency	1235
2761. Prime Pairs with Target Sum	1505
3233. Find the Count of Numbers Which Are Not Special	1509
2523. Closest Prime Numbers in Range	1650
2601. Prime Subtraction Operation	1779

§1.3 Prime Factorization

Problem	Rating
2521. Distinct Prime Factors of Product of Array	1413
2507. Smallest Value After Replacing with Sum of Prime Factors	1500
3326. Minimum Division Operations to Make Array Non Decreasing	1864
3629. Minimum Jumps to Reach End Via Prime Teleportation	2139
2584. Split the Array to Make Coprime Products	2159
3715. Sum of Perfect Square Ancestors	2235
2862. Maximum Element Sum of a Complete Subset of Indices	2292
2818. Apply Operations to Maximize Score	2397
1735. Count Ways to Make Array with Product	2500
2338. Count the Number of Ideal Arrays	2615

§1.4 Factorizing Factorials

Problem	Rating
172. Factorial Trailing Zeroes	Unrated

§1.5 Divisors

Problem	Rating
2427. Number of Common Factors	1172
1952. Three Divisors	1204
1492. The Kth Factor of N	1232
507. Perfect Number	Unrated
1390. Four Divisors	1478
1362. Closest Divisors	1534
829. Consecutive Numbers Sum	1694
3447. Assign Elements to Groups with Constraints	1731
3164. Find the Number of Good Pairs II	1777
2176. Count Equal AND Divisible Pairs in an Array	2200
2183. Count Array Pairs Divisible by K	2246

§1.6 Greatest Common Divisor (GCD)

Problem	Rating
1979. Find Greatest Common Divisor of Array	1184
3658. Gcd of Odd AND Even Sums	1220
2169. Count Operations to Obtain Zero	Unrated
914. X of a Kind in a Deck of Cards	1371
1071. Greatest Common Divisor of Strings	1398
2344. Minimum Deletions to Make Array Divisible	1641
365. Water AND Jug Problem	Unrated
2654. Minimum Number of Operations to Make All Array Elements Equal to 1	1929
1250. Check If It Is a Good Array	1983
149. Max Points on a Line	Unrated
1625. Lexicographically Smallest String After Applying Operations	1992
2607. Make K Subarray Sums Equal	2071
2447. Number of Subarrays with Gcd Equal to K	Unrated
2543. Check If Point Is Reachable	2221
3574. Maximize Subarray Gcd Score	2300
3312. Sorted Gcd Pair Queries	2533
1819. Number of Different Subsequences Gcds	2540
2807. Insert Greatest Common Divisors in Linked List	1279

§1.7 Least Common Multiple (LCM)

Problem	Rating
2413. Smallest Even Multiple	1145
858. Mirror Reflection	1881
2470. Number of Subarrays with Lcm Equal to K	Unrated

§1.8 Coprimality

Problem	Rating
1447. Simplified Fractions	1400
1766. Tree of Coprimes	2232
3411. Maximum Subarray with Equal Products	2300

§1.9 Modular Congruence

Problem	Rating
2453. Destroy Sequential Targets	1762
2598. Smallest Missing Non Negative Integer After Operations	1846

§1.10 Floor Division Blocks

Problem	Rating
1925. Count Square Sum Triples	Unrated

§1.11 Miscellaneous

Problem	Rating
1018. Binary Prefix Divisible by 5	1376
326. Power of Three	Unrated
372. Super Pow	Unrated
1015. Smallest Integer Divisible by K	Unrated
633. Sum of Square Numbers	Unrated
2240. Number of Ways to Buy Pens AND Pencils	Unrated

II. Combinatorics

§2.1 Rule of Product

Problem	Rating
1573. Number of Ways to Split a String	1591
2750. Ways to Split Array Into Good Subarrays	1598
2550. Count Collisions of Monkeys on a Polygon	1663
1922. Count Good Numbers	1675
2147. Number of Ways to Divide a Long Corridor	1915
2963. Count the Number of Good Partitions	1985
2306. Naming a Company	2305

§2.2 Combinatorial Counting

Problem	Rating
1175. Prime Arrangements	1489
3179. Find the N Th Value After K Seconds	Unrated
1359. Count All Valid Pickup AND Delivery Options	1723
3558. Number of Ways to Assign Edge Weights I	1845
2514. Count Anagrams	2070
1643. Kth Smallest Instructions	2080
2842. Count K Subsequences of a String with Maximum Beauty	2092
2221. Find Triangular Sum of an Array	Unrated
3463. Check If Digits Are Equal in String After Operations II	2286
1569. Number of Ways to Reorder Array to Get Same Bst	2288
3405. Count the Number of Arrays with K Matching Adjacent Elements	2310
3518. Smallest Palindromic Rearrangement II	2375
3272. Find the Count of Good Integers	2382
3317. Find the Number of Possible Ways for an Event	2414
3470. Permutations IV	2474
1830. Minimum Number of Operations to Make String Sorted	2620
2954. Count the Number of Infection Sequences	2645
3395. Subsequences with a Unique Middle Mode I	2800

§2.3 Balls into Boxes

Problem	Rating
1641. Count Sorted Vowel Strings	1519
1621. Number of Sets of K Non Overlapping Line Segments	2198
1735. Count Ways to Make Array with Product	2500
2338. Count the Number of Ideal Arrays	2615

§2.4 Inclusion-Exclusion Principle

Problem	Rating
2652. Sum Multiples	Unrated
2929. Distribute Candies Among Children II	Unrated

§2.5 Contribution Method

Problem	Rating
2063. Vowels of All Substrings	1663
1588. Sum of All Odd Length Subarrays	Unrated
2681. Power of Heroes	2060
891. Sum of Subsequence Widths	2183
3428. Maximum AND Minimum Sums of at Most Size K Subsequences	Unrated
3426. Manhattan Distances of All Arrangements of Pieces	2443
2763. Sum of Imbalance Numbers of All Subarrays	2700

III. Probability & Expected Value

Problem	Rating
1227. Airplane Seat Assignment Probability	Unrated

IV. Game Theory

Problem	Rating
292. Nim Game	Unrated
3227. Vowels Game in a String	1452
2038. Remove Colored Pieces If Both Neighbors Are the Same Color	1468
1686. Stone Game VI	2001
1927. Sum Game	2005
2029. Stone Game IX	2277

V. Computational Geometry

§5.1 Points and Lines

Problem	Rating
1232. Check If It Is a Straight Line	1247
2280. Minimum Lines to Represent a Line Chart	1681
1610. Maximum Number of Visible Points	2147

§5.2 Circles

Problem	Rating
1401. Circle AND Rectangle Overlapping	1709
1453. Maximum Number of Darts Inside of a Circular Dartboard	2202

§5.3 Rectangles and Polygons

Problem	Rating
836. Rectangle Overlap	1443
223. Rectangle Area	Unrated
593. Valid Square	Unrated
939. Minimum Area Rectangle	1752
963. Minimum Area Rectangle II	1991
3625. Count Number of Trapezoids II	2643

§5.4 Convex Hull

Problem	Rating
587. Erect the Fence	Unrated
812. Largest Triangle Area	Unrated

VI. Randomized Algorithms

§6.1 Random Numbers

Problem	Rating
398. Random Pick Index	Unrated
382. Linked List Random Node	Unrated
384. Shuffle an Array	Unrated
470. Implement Rand10 Using Rand7	Unrated
528. Random Pick with Weight	Unrated
710. Random Pick with Blacklist	Unrated
478. Generate Random Point in a Circle	Unrated
497. Random Point in Non Overlapping Rectangles	Unrated
519. Random Flip Matrix	Unrated
380. Insert Delete Getrandom O1	Unrated
381. Insert Delete Getrandom O1 Duplicates Allowed	Unrated

§6.2 Randomization Techniques

Problem	Rating
1317. Convert Integer to the Sum of Two No Zero Integers	1278
1968. Array with Elements Not Equal to Average of Neighbors	1499
1157. Online Majority Element in Subarray	2205
3680. Generate Schedule	2378

VII. Miscellaneous Mathematics

§7.1 Palindromic Numbers

Problem	Rating
9. Palindrome Number	Unrated
2396. Strictly Palindromic Number	1329
2217. Find Palindrome with Fixed Length	1822
866. Prime Palindrome	1938
2967. Minimum Cost to Make Array Equalindromic	2116
906. Super Palindromes	2140
2081. Sum of K Mirror Numbers	2210
3272. Find the Count of Good Integers	2382
564. Find the Closest Palindrome	Unrated
3646. Next Special Palindrome Number	2445
479. Largest Palindrome Product	Unrated

§7.2 Integer Partition

Problem	Rating
343. Integer Break	Unrated
1808. Maximize Number of Nice Divisors	2070

§7.3 Manhattan Distance

Problem	Rating
3443. Maximum Manhattan Distance After K Changes	1856
1131. Maximum of Absolute Value Expression	2059
3102. Minimize Manhattan Distances	2216
1330. Reverse Subarray to Maximize Array Value	2482

§7.4 Polynomials

Problem	Rating
611. Valid Triangle Number	Unrated
923. 3sum with Multiplicity	Unrated
835. Image Overlap	Unrated

§7.7 Miscellaneous

Problem	Rating
1523. Count Odd Numbers in an Interval Range	1209
1716. Calculate Money in Leetcode Bank	1295
2829. Determine the Minimum Sum of a K Avoiding Array	1347
2579. Count Total Number of Colored Cells	1356
3648. Minimum Sensors to Cover Grid	1396
2834. Find the Minimum Possible Sum of a Beautiful Array	1409
1414. Find the Minimum Number of Fibonacci Numbers Whose Sum Is K	1466
319. Bulb Switcher	1500
1780. Check If Number Is a Sum of Powers of Three	1506
3091. Apply Operations to Make Sum of Array Greater Than OR Equal to K	1522
3468. Find the Number of Copy Arrays	1545
2310. Sum of Numbers with Units Digit K	1559
2844. Minimum Operations to Make a Special Number	1588
2145. Count the Hidden Sequences	1614
2541. Minimum Operations to Make Array Equal II	1620
1502. Can Make Arithmetic Progression From Sequence	Unrated
2195. Append K Integers with Minimal Sum	1659
2457. Minimum Addition to Make Integer Beautiful	1680
1017. Convert to Base 2	1698
3649. Number of Perfect Pairs	1716
1954. Minimum Garden Perimeter to Collect Enough Apples	1759
1073. Adding Two Negabinary Numbers	1807
1823. Find the Winner of the Circular Game	1833
166. Fraction to Recurring Decimal	1833
3012. Minimize Length of Array Using Operations	1833
483. Smallest Good Base	Unrated
972. Equal Rational Numbers	2121
1739. Building Boxes	2198
2443. Sum of Number AND Its Reverse	Unrated
1806. Minimum Number of Operations to Reinitialize a Permutation	Unrated
458. Poor Pigs	Unrated
2117. Abbreviating the Product of a Range	2477

It sits seventh on Track 1, between Greedy Algorithms and Strings & Automata, and since the route never locks a plan you can jump here from the full catalog.

Ratings come from zerotrac's LeetCode contest ratings. Some problems have no zerotrac rating and are marked Unrated.

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