LeetCode Library

Catalog the drills. Don’t blog them.

The main blog stays essay-oriented. This section is the working archive: searchable, filterable, and built directly from the same daily source file.

1287 entries

1138 unique problems

5 years

25 patterns

812 with Rust

232 hard drills

Search archive Repeat lab Library RSS Raw archive Random entry

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Find the right drill fast

Search

Difficulty All Easy Medium Hard

Year All 2026 2025 2024 2023 2022

Language All Kotlin Rust

Pattern All Array Graph String Sorting Dynamic Programming Simulation Tree Binary Search Math Bit Manipulation Hash Map Two Pointers Stack Sliding Window Heap Backtracking Linked List Greedy Union Find Queue Prefix Sum Trie Intervals Monotonic Stack

Newest first across 1287 entries.

Study dashboard

Use the mix to pick difficulty, then jump into the strongest recurring routes.

Difficulty mix

Easy 309

Medium 746

Hard 232

Recent run

14 13 12 11 10 09 08 07 06 05 04 03 02 01

Top pattern routes

Array 385 Graph 214 String 205 Sorting 155 Dynamic Programming 99 Simulation 98 Tree 96 Binary Search 83

Practice signals

Repeated drills, long thinking traces, misses, and tiny solutions extracted from the daily notes.

Repeated drills 144 293 entries revisit the same problem id. Long thoughts 47 Entries with a long j thinking trace. Couldn’t solve cleanly 81 Marked with did not solve, could not solve, or give up language. Almost gave up 60 Minute markers plus hints, wrong answers, or explicit stopping points. One-liners 69 Shortest Kotlin or Rust solution is two nonblank lines or less. Comebacks 7 Repeated problems first marked stuck, then later solved cleaner.

One-liners 69 Tiny 399 Compact 447 Standard 286 Long 65 Unknown 21

Repeat ledger

Same problem, different date. The timeline compares solution length and thinking trace changes.

1980. Find Unique Binary String

3x

16.11.2023 to 08.03.2026

Lines -4 Chars -61 Thoughts 0

1. 16.11.2023 8 lines
2. 20.02.2025 3 lines
3. 08.03.2026 4 lines

2402. Meeting Rooms III

3x

18.02.2024 to 27.12.2025

Lines 0 Chars -73 Thoughts +17

1. 18.02.2024 10 lines
2. 11.07.2025 10 lines
3. 27.12.2025 10 lines , 17 thoughts

1930. Unique Length-3 Palindromic Subsequences

3x

14.11.2023 to 21.11.2025

Lines -8 Chars -168 Thoughts +4

1. 14.11.2023 11 lines
2. 04.01.2025 5 lines
3. 21.11.2025 3 lines , 4 thoughts

2444. Count Subarrays With Fixed Bounds

3x

04.03.2023 to 26.04.2025

Lines -68 Chars -1499 Thoughts +7

1. 04.03.2023 77 lines
2. 31.03.2024 10 lines , 28 thoughts
3. 26.04.2025 9 lines , 7 thoughts

1514. Path with Maximum Probability

3x

28.06.2023 to 31.08.2024

Lines -9 Chars -201 Thoughts 0

1. 28.06.2023 18 lines
2. 27.08.2024 15 lines
3. 31.08.2024 9 lines

1582. Special Positions in a Binary Matrix

2x

13.12.2023 to 04.08.2026

Lines -6 Chars -183 Thoughts 0

1. 13.12.2023 10 lines
2. 04.08.2026 4 lines

Couldn’t first, solved later

2033. Minimum Operations to Make a Uni-Value Grid 26.03.2025 to 28.04.2026 1590. Make Sum Divisible by P 03.10.2024 to 30.11.2025 2872. Maximum Number of K-Divisible Components 21.12.2024 to 28.11.2025 407. Trapping Rain Water II 19.01.2025 to 03.10.2025 1792. Maximum Average Pass Ratio 15.12.2024 to 01.09.2025 368. Largest Divisible Subset 09.02.2024 to 06.04.2025

Honest slices

Useful edge categories for choosing what to revisit next.

Long j sections

• 1611. Minimum One Bit Operations to Make Integers Zero 86 thought lines, 45 min
• 2561. Rearranging Fruits 80 thought lines, 29 min
• 3480. Maximize Subarrays After Removing One Conflicting Pair 72 thought lines, 36 min
• 761. Special Binary String 67 thought lines, 30 min
• 3660. Jump Game IX 65 thought lines, 61 min
• 3495. Minimum Operations to Make Array Elements Zero 64 thought lines, 44 min

Couldn’t solve

• 1665. Minimum Initial Energy to Finish Tasks 12.05.2026, 26 min
• 3225. Maximum Score From Grid Operations 29.04.2026, 78 min
• 3464. Maximize the Distance Between Points on a Square 25.04.2026, 70 min
• 2615. Sum of Distances 23.04.2026
• 2463. Minimum Total Distance Traveled 14.04.2026, 30 min
• 3655. XOR After Range Multiplication Queries II 09.04.2026, 58 min

Almost gave up

• 1900. The Earliest and Latest Rounds Where Players Compete 103 min, 40 thought lines
• 664. Strange Printer 90 min, 9 thought lines
• 3225. Maximum Score From Grid Operations 78 min, 7 thought lines
• 1039. Minimum Score Triangulation of Polygon 76 min, 40 thought lines
• 3445. Maximum Difference Between Even and Odd Frequency II 75 min, 38 thought lines
• 3343. Count Number of Balanced Permutations 75 min, 24 thought lines

Smallest solutions

• 344. Reverse String 1 lines, 45 chars, kotlin
• 1780. Check if Number is a Sum of Powers of Three 1 lines, 54 chars, kotlin
• 342. Power of Four 1 lines, 88 chars, kotlin
• 1822. Sign of the Product of an Array 1 lines, 102 chars, kotlin
• 1269. Number of Ways to Stay in the Same Place After Some Steps 2 lines, 47 chars, kotlin
• 1846. Maximum Element After Decreasing and Rearranging 2 lines, 47 chars, kotlin

Browse the map

Start with a year, a language, or one of the recurring patterns.

Years

• 2026131
• 2025365
• 2024366
• 2023363
• 202262

Languages

• Kotlin1281
• Rust812

Collections

• Repeat Lab144
• Comebacks7
• Long Thoughts47
• Could Not Solve81
• Pressure Log60
• Small Code69

Patterns

• Array385
• Graph214
• String205
• Sorting155
• Dynamic Programming99
• Simulation98
• Tree96
• Binary Search83
• Math76
• Bit Manipulation75
• Hash Map66
• Two Pointers61
• Stack52
• Sliding Window51
• Heap44
• Backtracking37
• Linked List37
• Greedy33
• Union Find33
• Queue28
• Prefix Sum20
• Trie17
• Intervals15
• Monotonic Stack13

Archive

Newest first. Start broad, then filter down. Each entry opens the full post for that day.

14.05.2026

easy

2784. Check if Array is Good

Kotlin Rust

Is combination 1..n,n

Array

array sorting array-index marking in-place index marking arrays

Full post LeetCode Kotlin Rust YouTube Telegram

13.05.2026

medium

1674. Minimum Moves to Make Array Complementary

Kotlin Rust

Min changes 1..L to make complementary pair sum equal

Array

array line sweep difference array interval merging arrays

Full post LeetCode Kotlin Rust YouTube Telegram

12.05.2026

hard

1665. Minimum Initial Energy to Finish Tasks

Kotlin Rust

Energy for all tasks (spend, limit)

Binary Search Greedy Sorting

array binary search greedy sorting folding (reduce) sorting by custom key

Full post LeetCode Kotlin Rust YouTube Telegram

11.05.2026

easy

2553. Separate the Digits in an Array

Kotlin Rust

LIst of numbers to list of digits

Array

array string conversion string conversion and mapping arrays

Full post LeetCode Kotlin Rust YouTube Telegram

10.05.2026

medium

2770. Maximum Number of Jumps to Reach the Last Index

Kotlin Rust

Max steps to reach end by jumps n[j]-n[i] in -t..t

Dynamic Programming Graph Tree

segment tree array dynamic programming binary search range query with segment tree top-down and bottom-up dp

Full post LeetCode Kotlin Rust YouTube Telegram

09.05.2026

medium

1914. Cyclically Rotating a Grid

Kotlin Rust

Rotate matix layers by k

Array

matrix array rotation 3-reversal trick arrays

Full post LeetCode Kotlin Rust YouTube Telegram

08.05.2026

medium

3629. Minimum Jumps to Reach End via Prime Teleportation

Kotlin Rust

Shortest path by prime factors

Graph Hash Map Math

hash map queue hash set breadth-first search sieve of eratosthenes prime factorization

Full post LeetCode Kotlin Rust YouTube Telegram

07.05.2026

medium

3660. Jump Game IX

Kotlin Rust

Max on path jumping left-up and right-down

Binary Search Queue Array

array monotonic queue dynamic programming binary search two-pass scanning monotonic queue usage

Full post LeetCode Kotlin Rust YouTube Telegram

06.05.2026

medium

1861. Rotating the Box

Kotlin Rust

Rotate and simulate gravity in matrix

Simulation Array

matrix sorting split and sort segments arrays

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05.05.2026

medium

61. Rotate List

Kotlin Rust

Rotate linked list k steps

Linked List

linked list linked list manipulation cycle formation in linked list modulo arithmetic for rotation offset

Full post LeetCode Kotlin Rust YouTube Telegram

04.05.2026

medium

48. Rotate Image

Kotlin Rust

Rotate square matrix

Array

matrix in-place matrix rotation matrix transpose matrix reversal layer by layer 4-way swap reverse and transpose

Full post LeetCode Kotlin Rust YouTube Telegram

03.05.2026

easy

796. Rotate String

Kotlin Rust

Match strings after rotation

String Array

knuth-morris-pratt (kmp) string matching two-way string matching string concatenation for rotation check strings

Full post LeetCode Kotlin Rust YouTube Telegram

02.05.2026

medium

788. Rotated Digits

Kotlin Rust

Count numbers in 0..n with mirrored digits 2-5 6-9, 0,1,8, but not 3,4,7

brute force mathematical counting regex filtering digit subtree counting number theory strings

Full post LeetCode Kotlin Rust YouTube Telegram

01.05.2026

medium

396. Rotate Function

Kotlin Rust

Max rolling hash

array rolling hash rolling hash reuse arrays

Full post LeetCode Kotlin Rust YouTube Telegram

30.04.2026

medium

3742. Maximum Path Score in a Grid

Kotlin Rust

Max right-bottom path value with at most k cost

Dynamic Programming Array

hash map matrix dynamic programming recursion with memoization memoization bottom-up dp

Full post LeetCode Kotlin Rust YouTube

29.04.2026

hard

3225. Maximum Score From Grid Operations

Kotlin Rust

Max sum adjacent to marked columns

Array

hash map matrix dynamic programming depth-first search with memoization prefix sums memoization

Full post LeetCode Kotlin Rust YouTube Telegram

28.04.2026

medium

2033. Minimum Operations to Make a Uni-Value Grid

Kotlin Rust

Min ops to make all numbers equal by +-X

Array

matrix array median-based optimization sorting modulo-invariant grouping flattening matrix to array

Full post LeetCode Kotlin Rust YouTube Telegram

27.04.2026

medium

1391. Check if There is a Valid Path in a Grid

Kotlin Rust

Path 0 to end on type-cells 2D grid

Union Find Array

union-find matrix graph traversal transition matrix path validation via direction transitions graphs

Full post LeetCode Kotlin Rust YouTube Telegram

26.04.2026

medium

1559. Detect Cycles in 2D Grid

Kotlin Rust

Check cycle in 2D grid

Union Find Graph Bit Manipulation

union-find array union-find-path-compression row-by-row-connection graph arrays

Full post LeetCode Kotlin Rust YouTube Telegram

25.04.2026

hard

3464. Maximize the Distance Between Points on a Square

Kotlin Rust

Max of minimum distnace between selected k points on square perimeter

Binary Search Sorting

array binary search perimeter flattening wrap-around handling geometry

Full post LeetCode Kotlin Rust YouTube Telegram

24.04.2026

easy

2833. Furthest Point From Origin

Kotlin Rust

Max dist when replace with L or R

Math

counting mathematical formula simplification strings

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23.04.2026

medium

2615. Sum of Distances

Kotlin Rust

Sum of distances to each occurance

hash-map array prefix-sum two-pointer iteration prefix sums with frequency tracking arrays

Full post LeetCode Kotlin Rust YouTube Telegram

22.04.2026

medium

2452. Words Within Two Edits of Dictionary

Kotlin Rust

Words in dictionary with 2 edits

Hash Map

hash set brute force character difference counting strings

Full post LeetCode Kotlin Rust YouTube Telegram

21.04.2026

medium

1722. Minimize Hamming Distance After Swap Operations

Kotlin Rust

Diff src vs target after rearrange by rules

Union Find Sorting

union-find hash map array counting sort path compression frequency counting

Full post LeetCode Kotlin Rust YouTube Telegram

20.04.2026

easy

2078. Two Furthest Houses With Different Colors

Kotlin Rust

Max distance between different numbers

array int array greedy two pointers arrays

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19.04.2026

medium

1855. Maximum Distance Between a Pair of Values

Kotlin Rust

Max distance a[i] not greater than b[j] window

Sliding Window

array list sliding window binary search arrays

Full post LeetCode Kotlin Rust YouTube Telegram

18.04.2026

easy

3783. Mirror Distance of an Integer

Kotlin Rust

Diff with reversal

Full post LeetCode Kotlin Rust YouTube Telegram

17.04.2026

medium

3761. Minimum Absolute Distance Between Mirror Pairs

Kotlin Rust

Distance to prev mirror number

Hash Map

hash-map one-pass string-reversal arrays

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16.04.2026

medium

3488. Closest Equal Element Queries

Kotlin Rust

Shortest distances to the same values

hash-map array two-pass circular-array arrays

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15.04.2026

easy

2515. Shortest Distance to Target String in a Circular Array

Kotlin Rust

Distance to target

String Array

array circular-indexing arrays strings

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14.04.2026

hard

2463. Minimum Total Distance Traveled

Kotlin Rust

Shortest distances to travel robots to factories

Dynamic Programming Simulation

hash-map array dynamic-programming recursion sorting arrays

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13.04.2026

easy

1848. Minimum Distance to the Target Element

Kotlin Rust

Distance to target from start

array arrays

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12.04.2026

hard

1320. Minimum Distance to Type a Word Using Two Fingers

Kotlin Rust

Min travel on keyboard to type a word

Dynamic Programming String

array dynamic-programming strings

Full post LeetCode Kotlin Rust YouTube Telegram

11.04.2026

medium

3741. Minimum Distance Between Three Equal Elements II

Kotlin Rust

Min sum of distances between i,j,k of the same values

hash-map array sliding-window bit-manipulation arrays

Full post LeetCode YouTube Telegram

10.04.2026

easy

3740. Minimum Distance Between Three Equal Elements I

Kotlin Rust

Min sum of distances between i,j,k of the same values

hash map sliding window group by value arrays

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09.04.2026

hard

3655. XOR After Range Multiplication Queries II

Kotlin Rust

Run stepped multiplication queries

Bit Manipulation Math

array 2d array modular exponentiation prefix product sqrt decomposition modular inverse via fermat's little theorem

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08.04.2026

medium

3653. XOR After Range Multiplication Queries I

Kotlin Rust

Run queries

Bit Manipulation

array brute force in-place modification arrays

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07.04.2026

medium

2069. Walking Robot Simulation II

Kotlin Rust

Implement perimeter-robot

Simulation

array modular arithmetic perimeter flattening simulation

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06.04.2026

medium

874. Walking Robot Simulation

Kotlin Rust

Farthest robot movement

Simulation

hash set simulation coordinate compression geometry arrays

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05.04.2026

easy

657. Robot Return to Origin

Kotlin Rust

R,L,U,D return to 0 in XY plane

Simulation

counting modular arithmetic mapping strings arrays

Full post LeetCode YouTube Telegram

04.04.2026

medium

2075. Decode the Slanted Ciphertext

Kotlin Rust

Decode row-encoded string

String

string string traversal trim trailing spaces strings

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03.04.2026

hard

3661. Maximum Walls Destroyed by Robots

Kotlin

Max walls hit, each robot shoot left or right

Dynamic Programming Simulation

hash map array dynamic programming binary search depth-first search memoization

Full post LeetCode Kotlin YouTube Telegram

02.04.2026

medium

3418. Maximum Amount of Money Robot Can Earn

Kotlin Rust

Max sum path, 2 skips allowed

Dynamic Programming Graph Simulation

matrix hash map dynamic programming depth-first search with memoization state compression top-down memoization

Full post LeetCode YouTube Telegram

01.04.2026

hard

2751. Robot Collisions

Kotlin Rust

Collide LR robots

Stack Sorting Simulation

stack array sorting in-place stack simulation collision simulation simulation

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31.03.2026

hard

3474. Lexicographically Smallest Generated String

Kotlin Rust

String from pattern matches

Greedy String

array string greedy pattern matching increment rightmost letter strings

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30.03.2026

medium

2840. Check if Strings Can be Made Equal With Operations II

Kotlin Rust

Strings equal at odd-even positions

hashing parity-based hashing strings

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29.03.2026

easy

2839. Check if Strings Can be Made Equal With Operations I

Kotlin Rust

Match a and b at (0|2,1|3) positions

set bitmasking set operations set comparison strings

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28.03.2026

hard

2573. Find the String with LCP

Kotlin Rust

Build string from longest common prefixes matrix

Dynamic Programming String Array

matrix array dynamic programming matrix symmetry and diagonal properties character assignment with validation strings

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27.03.2026

easy

2946. Matrix Similarity After Cyclic Shifts

Kotlin Rust

Shift rows k times left and right

Simulation Array

matrix modular arithmetic modular indexing for cyclic shifts arrays

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26.03.2026

hard

3548. Equal Sum Grid Partition II

Kotlin Rust

Cut matrix in half sums, can remove one cell

Hash Map Array

hash-map matrix prefix-sum hashing iteration rotations to simplify logic

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25.03.2026

medium

3546. Equal Sum Grid Partition I

Kotlin Rust

Split matrix to equal sums

Array

matrix hash set prefix sum single pass prefix sum with early stopping arrays

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24.03.2026

medium

2906. Construct Product Matrix

Kotlin Rust

Product of other cells in a matrix

Prefix Sum Math Array

matrix prefix-sum flattening matrix prefix and suffix product arrays modular arithmetic without division arrays

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23.03.2026

medium

1594. Maximum Non Negative Product in a Matrix

Kotlin Rust

Max product path right-down

Dynamic Programming Array

matrix array dynamic programming tracking max and min states space optimization with 1D array arrays

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22.03.2026

easy

1886. Determine Whether Matrix Can Be Obtained By Rotation

Kotlin Rust

Rotate matrix

Array

matrix matrix rotation rotation by 90 degrees arrays

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21.03.2026

medium

3643. Flip Square Submatrix Vertically

Kotlin Rust

Reverse submatrix k by k

matrix in-place matrix manipulation slice swapping arrays

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20.03.2026

medium

3567. Minimum Absolute Difference in Sliding Submatrix

Kotlin Rust

Mid diffs in k k submatrices

Array

matrix sorted set sliding window sorting windowed iteration deduplication

Full post LeetCode Kotlin Rust YouTube Telegram

19.03.2026

medium

3212. Count Submatrices With Equal Frequency of X and Y

Kotlin Rust

Count prefix freq X == freq Y

Array

matrix array prefix sums balance tracking bitmasking arrays

Full post LeetCode Kotlin Rust YouTube Telegram

18.03.2026

medium

3070. Count Submatrices with Top-Left Element and Sum Less Than k

Kotlin Rust

Count prefix sums less than K

Prefix Sum Array

matrix prefix sum in-place prefix sum computation early stopping optimization arrays

Full post LeetCode Kotlin Rust YouTube Telegram

17.03.2026

medium

1727. Largest Submatrix With Rearrangements

Kotlin Rust

Max area of binary matrix, swap columns

Sorting Array

matrix array sorting dynamic programming histogram transformation sorting histogram rows

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16.03.2026

medium

1878. Get Biggest Three Rhombus Sums in a Grid

Kotlin Rust

Top 3 rhombus sums

Array

matrix brute-force coordinate traversal arrays geometry

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15.03.2026

hard

1622. Fancy Sequence

Kotlin Rust

Design: add number, mulriply all, add all

dynamic array modular arithmetic modular inverse design

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14.03.2026

medium

1415. The k-th Lexicographical String of All Happy Strings of Length n

Kotlin Rust

K-th generated abc non-repeating string

Graph Sorting String

depth-first search counting subtrees to index lexicographical order strings

Full post LeetCode Kotlin Rust YouTube Telegram

13.03.2026

medium

3296. Minimum Number of Seconds to Make Mountain Height Zero

Kotlin Rust

Min steps to work a mountain with arithmetic-sum-workers

Binary Search

array binary search arithmetic sum precomputation nested binary search math search

Full post LeetCode Kotlin Rust YouTube Telegram

12.03.2026

hard

3600. Maximize Spanning Tree Stability with Upgrades

Kotlin Rust

Max of min values in span tree of graph, 2 s at most k

Graph Tree Binary Search

union-find array greedy binary search sorting by multiple keys cycle detection

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11.03.2026

easy

1009. Complement of Base 10 Integer

Kotlin Rust

Invert binary

bit manipulation bitmask with next power of two minus one bitwise operations

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10.03.2026

hard

3130. Find All Possible Stable Binary Arrays II

Kotlin Rust

array to make with z zeros, o ones, l repeats

Dynamic Programming Array

hash map dynamic programming combinatorics inclusion-exclusion principle modular arithmetic memoization

Full post LeetCode Kotlin Rust YouTube Telegram

09.03.2026

medium

3129. Find All Possible Stable Binary Arrays I

Kotlin

Count 01-arrays with z zeros, o ones, at most l repeat

hash map depth-first search with memoization state flipping in recursion memoization to avoid recomputation dynamic programming combinatorics

Full post LeetCode Kotlin YouTube Telegram

08.03.2026

medium

1980. Find Unique Binary String

Kotlin Rust

Uniq bits not in a set

Bit Manipulation String

array bit manipulation xor trick strings combinatorics

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07.03.2026

medium

1888. Minimum Number of Flips to Make the Binary String Alternating

Kotlin Rust

Min flips to make 01 alterating string sum window

Prefix Sum Sliding Window Bit Manipulation

array prefix sum sliding window modulo indexing for rotation bit parity check strings

Full post LeetCode Kotlin Rust YouTube Telegram

06.03.2026

easy

1784. Check if Binary String Has at Most One Segment of Ones

Kotlin Rust

+0 pattern

String

string string search substring search strings

Full post LeetCode Kotlin Rust YouTube Telegram

05.03.2026

easy

1758. Minimum Changes To Make Alternating Binary String

Kotlin Rust

Min flips to make bits alterating

Bit Manipulation String

arithmetic counting parity check strings

Full post LeetCode Kotlin Rust YouTube Telegram

04.08.2026

easy

1582. Special Positions in a Binary Matrix

Kotlin Rust

Count single 1-row-column

Array

matrix brute force row and column sum checks arrays

Full post LeetCode Kotlin Rust YouTube Telegram

03.03.2026

medium

1545. Find Kth Bit in Nth Binary String

Kotlin Rust

Kth bit in s=s+1+inv(rev(s)) sequence

Bit Manipulation String

bit manipulation recursion divide and conquer highest one bit extraction pattern observation bitwise parity check

Full post LeetCode Kotlin Rust YouTube Telegram

02.03.2026

medium

1536. Minimum Swaps to Arrange a Binary Grid

Kotlin Rust

Min rows swaps to zero above diagonal

Array

matrix array greedy bubble sort suffix counting greedy rearrangement

Full post LeetCode Kotlin Rust YouTube Telegram

01.03.2026

medium

1689. Partitioning Into Minimum Number Of Deci-Binary Numbers

Kotlin Rust

Min 01-strings add up to target

Greedy

greedy max element selection strings

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28.02.2026

medium

1680. Concatenation of Consecutive Binary Numbers

Kotlin Rust

Concat binaries 1..n

Array

matrix bit manipulation matrix exponentiation fold/reduce count leading zero bits modular arithmetic

Full post LeetCode Kotlin Rust YouTube Telegram

27.02.2026

hard

3666. Minimum Operations to Equalize Binary String

Kotlin

Min steps to convert 01 stirng to ones flipping K

Graph Bit Manipulation String

array breadth-first search dynamic programming parity optimization state space pruning strings

Full post LeetCode Kotlin YouTube Telegram

26.02.2026

medium

1404. Number of Steps to Reduce a Number in Binary Representation to One

Kotlin Rust

Ops /2+1 to make 1

Simulation

simulation carry propagation optimization strings

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25.02.2026

easy

1356. Sort Integers by The Number of 1 Bits

Kotlin Rust

Sort

Sorting Bit Manipulation

array sorting bit counting arrays

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24.02.2026

easy

1022. Sum of Root To Leaf Binary Numbers

Kotlin Rust

Sum of a binary numbers in a binary tree

Tree

binary tree depth-first search in-place value accumulation trees binary numbers

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23.02.2026

medium

1461. Check If a String Contains All Binary Codes of Size K

Kotlin Rust

All numbers as substring length of k window

Sliding Window String

hash set sliding window early return optimization strings

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22.02.2026

easy

868. Binary Gap

Kotlin Rust

Distance between onces in a binary

String

string bit manipulation string scanning bitwise operations to find set bits regex pattern matching on binary strings

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21.02.2026

easy

762. Prime Number of Set Bits in Binary Representation

Kotlin Rust

Number in l..r with prime bits count

Bit Manipulation Simulation Math

combinatorics bit-manipulation gosper's hack prime bitmask filtering combinatorial counting

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20.02.2026

hard

761. Special Binary String

Kotlin

Swaps of 1M0-special substring to make string large

String

string list recursion divide and conquer sorting balance counting

Full post LeetCode Kotlin YouTube Telegram

19.02.2026

easy

696. Count Binary Substrings

Kotlin Rust

Count substrings of 01 and 10 window

Sliding Window

string sliding window run length grouping strings

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18.02.2026

easy

693. Binary Number with Alternating Bits

Kotlin Rust

Alternating bits

Bit Manipulation Simulation

bit manipulation bitwise shift and mask bitwise xor and and operations bits

Full post LeetCode Kotlin Rust YouTube Telegram

17.02.2026

easy

401. Binary Watch

Kotlin Rust

All times with count bits set

Backtracking Bit Manipulation

bitmask bit manipulation backtracking brute force bit counting next smallest bitmask generation

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16.02.2026

easy

190. Reverse Bits

Kotlin Rust

Reverse bits

Bit Manipulation

bit manipulation lookup table optimization built-in function usage bits

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15.02.2026

easy

67. Add Binary

Kotlin Rust

Binary strings sum

string bit manipulation carry handling reverse iteration strings arithmetic

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14.02.2026

medium

799. Champagne Tower

Kotlin Rust

Flow in a Pascal's Triangle

Simulation

array simulation arena allocation right-aligned pyramid iteration dynamic programming math

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13.02.2026

medium

3714. Longest Balanced Substring II

Kotlin Rust

Largest equal frequencies substring of abc-string

Hash Map String

hash-map array hashing prefix-sum sliding-window difference encoding

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12.02.2026

medium

3713. Longest Balanced Substring I

Kotlin Rust

Max substring with equal frequencies window

Sliding Window String

array sliding window frequency counting strings

Full post LeetCode Kotlin Rust YouTube Telegram

11.02.2026

hard

3721. Longest Balanced Subarray II

Kotlin Rust

Max subarray evens count = odds count tree

Tree Prefix Sum

segment tree array binary search prefix sum transformation binary search on answer handling duplicates in segment tree

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10.02.2026

medium

3719. Longest Balanced Subarray I

Kotlin Rust

Longes even=odd subarray

hash set array brute force prefix sums two pointers arrays

Full post LeetCode Kotlin Rust YouTube Telegram

09.02.2026

medium

1382. Balance a Binary Search Tree

Kotlin Rust

Balance binary search tree

Graph Tree Binary Search

binary search tree list stack depth-first search in-order traversal in-order traversal to sorted list

Full post LeetCode Kotlin Rust YouTube Telegram

08.02.2026

easy

110. Balanced Binary Tree

Kotlin Rust

Is tree balanced?

Graph Tree

binary tree depth-first search short-circuit evaluation post-order traversal trees

Full post LeetCode Kotlin Rust YouTube Telegram

07.02.2026

medium

1653. Minimum Deletions to Make String Balanced

Kotlin Rust

Min removal to balance 'ab'

Greedy String

greedy counting and split partitioning strings

Full post LeetCode Kotlin Rust YouTube Telegram

06.02.2026

medium

3634. Minimum Removals to Balance Array

Kotlin Rust

Min removals to make min k not less than max window

Sliding Window Array

array sliding window lazy sliding window arrays

Full post LeetCode Kotlin Rust YouTube Telegram

05.02.2026

easy

3379. Transformed Array

Kotlin Rust

Shuffled list i+n[i]

Array

array modular arithmetic in-place transformation with modular indexing arrays

Full post LeetCode Kotlin Rust YouTube Telegram

03.02.2026

easy

3637. Trionic Array I

Kotlin Rust

Validate inc,dec,inc sequency

Array

array pattern matching sliding window regex pattern matching chunking consecutive elements arrays

Full post LeetCode Kotlin Rust YouTube Telegram

02.02.2026

hard

3013. Divide an Array Into Subarrays With Minimum Cost II

Kotlin

Min sum of k splits at max d distance window

Heap Sliding Window Array

treeset binary indexed tree sliding window dynamic programming binary search two balanced containers

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01.02.2026

easy

3010. Divide an Array Into Subarrays With Minimum Cost I

Kotlin Rust

Split on 2 min values

Sorting Array

array sorting partial sorting arrays

Full post LeetCode Kotlin Rust YouTube Telegram

31.01.2026

easy

744. Find Smallest Letter Greater Than Target

Kotlin Rust

Larger letter in array

Binary Search Array

array binary search wrap-around indexing arrays

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30.01.2026

hard

2977. Minimum Cost to Convert String II

Kotlin

Min cost to convert string with transitions of substrings

Dynamic Programming Trie String

trie hash map array dynamic programming floyd-warshall rolling hash

Full post LeetCode Kotlin YouTube Telegram

29.01.2026

medium

2976. Minimum Cost to Convert String I

Kotlin Rust

Min cost to convert string

String Array

matrix floyd-warshall path relaxation strings

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28.01.2026

hard

3651. Minimum Cost Path with Teleportations

Kotlin Rust

Min cost to walk 2D grid with free teleports

Dynamic Programming Graph Array

matrix priority queue dijkstra dynamic programming state expansion with teleport count batch relaxation by sorted values

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27.01.2026

medium

3650. Minimum Cost Path with Edge Reversals

Kotlin Rust

Min path in weighted graph with reverse 2w nodes

Graph

graph priority-queue dijkstra graph-augmentation visited-flag-optimization graphs

Full post LeetCode Kotlin Rust YouTube Telegram

26.01.2026

easy

1200. Minimum Absolute Difference

Kotlin Rust

Min diff pairs

Sorting

array sorting sliding window group by and min aggregation arrays

Full post LeetCode Kotlin Rust YouTube Telegram

25.01.2026

easy

1984. Minimum Difference Between Highest and Lowest of K Scores

Kotlin Rust

Min k-diff window

Sliding Window Sorting

array sliding window sorting windowing with zip and skip arrays

Full post LeetCode Kotlin Rust YouTube Telegram

24.01.2026

medium

1877. Minimize Maximum Pair Sum in Array

Kotlin Rust

Min max pair

Sorting Array

array sorting two pointers arrays

Full post LeetCode Kotlin Rust YouTube Telegram

23.01.2026

hard

3510. Minimum Pair Removal to Sort Array II

Kotlin

Sort by removing min-sum pairs

Heap Sorting Array

linked list heap array priority queue greedy sentinel nodes

Full post LeetCode Kotlin YouTube Telegram

22.01.2026

easy

3507. Minimum Pair Removal to Sort Array I

Kotlin Rust

Sort by removing lowest sum pairs

Sorting Simulation Array

array simulation greedy pair removal arrays

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21.01.2026

medium

3315. Construct the Minimum Bitwise Array II

Kotlin Rust

Reverse operation x or (x+1)

Bit Manipulation Array

bit manipulation rightmost zero bit flip bits

Full post LeetCode Kotlin Rust YouTube Telegram

20.01.2026

easy

3314. Construct the Minimum Bitwise Array I

Kotlin Rust

Reverse x | (x+1) operation on prime numbers

Bit Manipulation Math Array

bit manipulation bitwise suffix clearing bitwise operations

Full post LeetCode Kotlin Rust YouTube Telegram

19.01.2025

medium

1292. Maximum Side Length of a Square with Sum Less than or Equal to Threshold

Kotlin Rust

Max square with sum less than threshold

Prefix Sum

matrix array prefix sum binary search prefix sum optimization incremental size checking

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18.01.2026

medium

1895. Largest Magic Square

Kotlin Rust

Max magic square

matrix brute force prefix sums arrays

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17.01.2026

medium

3047. Find the Largest Area of Square Inside Two Rectangles

Kotlin Rust

Max square in intersection

array brute force binary search line sweep interval intersection early loop termination

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16.01.2026

medium

2975. Maximum Square Area by Removing Fences From a Field

Kotlin Rust

Max square after remove vertical or horizontal bars

hash set set intersection brute force gap enumeration intersection of sets arrays

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15.01.2026

medium

2943. Maximize Area of Square Hole in Grid

Kotlin Rust

Max square area after removing bars in a grid

Hash Map Sorting Array

hash map array interval counting sorting consecutive interval counting arrays

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14.01.2026

hard

3454. Separate Squares II

Kotlin Rust

Min y to equal split areas exclude intersections sweep

array list line sweep sorting interval merging event sorting

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