LeetCode playbook

rearrange array in wiggle pattern (nums[0] < nums[1] > nums[2] < ...) using sorted interleaving.

count paths from top-left to bottom-right with obstacles using dp with space optimization to O(n).

quick reference for walking robot simulation. more notes soon.

find the largest plus sign order by computing longest consecutive 1s in four directions using dp.

quick reference for movie rating. more notes soon.

find minimum balls needed to clear board using dfs with memoization, trying to form groups of 3+.

quick reference for game theory. more notes soon.

find maximum number of points that lie on the same line using slope calculation and hash map.

distribute candy to children based on ratings using two-pass greedy approach.

implement RecentCounter using circular queue to count requests within last 3000ms.

find the largest palindrome made from the product of two n-digit numbers using brute force with optimizations.

find the largest square of 1s in a binary matrix using dynamic programming.

find minimum largest sum when splitting array into k subarrays using binary search on answer.

build balanced bst from sorted array by recursively using middle element as root.

quick reference for special array i. more notes soon.

implement least frequently used cache with O(1) operations using hash maps and doubly linked lists.

find shortest transformation sequence from beginWord to endWord using bfs.

binary search on a sorted 2d matrix by treating it as a flattened sorted array.

quick reference for maximum xor with an element from array. more notes soon.

find all pairs of words that form palindrome when concatenated by checking all prefix/suffix splits.

find median for each sliding window using sorted list to maintain window in sorted order.

rearrange array so no element equals the average of its neighbors using sorted interleaving pattern.

quick reference for addtwonumbers. more notes soon.

validate if string represents a valid number using state machine or regex.

set entire row and column to zero when element is zero, using first row and column as markers for O(1) space.

quick reference for kth smallest in lexicographical order. more notes soon.

quick reference for palindrome partitioning ii. more notes soon.

check if a grid can be fully covered by stamps using prefix sums and 2d difference array.

count total number of digit 1 appearing in all numbers from 1 to n using digit dp or mathematical analysis.

find minimum steps to make password strong by handling length, character types, and repeating sequences.

quick reference for 1 bit and 2 bit characters. more notes soon.

quick reference for 0001 two sum. more notes soon.

quick reference for 0007 reverse integer. more notes soon.

quick reference for 0009 palindrome number. more notes soon.

quick reference for 0013 roman to integer. more notes soon.

quick reference for 0014 longest common prefix. more notes soon.

quick reference for 0020 valid parentheses. more notes soon.

quick reference for 0021 merge two sorted lists. more notes soon.

quick reference for 0026 remove duplicates from sorted array. more notes soon.

quick reference for 0027 remove element. more notes soon.

quick reference for 0028 find the index of the first occurrence in a string. more notes soon.

quick reference for 0035 search insert position. more notes soon.

quick reference for 0058 length of last word. more notes soon.

quick reference for 0066 plus one. more notes soon.

quick reference for 0067 add binary. more notes soon.

quick reference for 0069 sqrtx. more notes soon.

quick reference for 0070 climbing stairs. more notes soon.

quick reference for 0083 remove duplicates from sorted list. more notes soon.

quick reference for 0088 merge sorted array. more notes soon.

quick reference for 0094 binary tree inorder traversal. more notes soon.

quick reference for 0100 same tree. more notes soon.

quick reference for 0101 symmetric tree. more notes soon.

quick reference for 0104 maximum depth of binary tree. more notes soon.

quick reference for 0107 binary tree level order traversal ii. more notes soon.

quick reference for 0108 convert sorted array to binary search tree. more notes soon.

quick reference for 0110 balanced binary tree. more notes soon.

quick reference for 0111 minimum depth of binary tree. more notes soon.

quick reference for 0112 path sum. more notes soon.

quick reference for 0118 pascals triangle. more notes soon.

quick reference for 0119 pascals triangle ii. more notes soon.

quick reference for 0121 best time to buy and sell stock. more notes soon.

quick reference for 0125 valid palindrome. more notes soon.

quick reference for 0136 single number. more notes soon.

quick reference for 0141 linked list cycle. more notes soon.

quick reference for 0144 binary tree preorder traversal. more notes soon.

quick reference for 0145 binary tree postorder traversal. more notes soon.

quick reference for 0155 min stack. more notes soon.

quick reference for 0160 intersection of two linked lists. more notes soon.

quick reference for 0168 excel sheet column title. more notes soon.

quick reference for 0169 majority element. more notes soon.

quick reference for 0171 excel sheet column number. more notes soon.

quick reference for 0190 reverse bits. more notes soon.

quick reference for 0191 number of 1 bits. more notes soon.

quick reference for 0202 happy number. more notes soon.

quick reference for 0203 remove linked list elements. more notes soon.

quick reference for 0205 isomorphic strings. more notes soon.

quick reference for 0206 reverse linked list. more notes soon.

quick reference for 0217 contains duplicate. more notes soon.

quick reference for 0219 contains duplicate ii. more notes soon.

quick reference for 0222 count complete tree nodes. more notes soon.

quick reference for 0225 implement stack using queues. more notes soon.

quick reference for 0226 invert binary tree. more notes soon.

quick reference for 0228 summary ranges. more notes soon.

quick reference for 0231 power of two. more notes soon.

quick reference for 0232 implement queue using stacks. more notes soon.

quick reference for 0234 palindrome linked list. more notes soon.

quick reference for 0235 lowest common ancestor of a binary search tree. more notes soon.

quick reference for 0237 delete node in a linked list. more notes soon.

quick reference for 0242 valid anagram. more notes soon.

quick reference for 0257 binary tree paths. more notes soon.

quick reference for 0258 add digits. more notes soon.

quick reference for 0263 ugly number. more notes soon.

quick reference for 0268 missing number. more notes soon.

quick reference for 0278 first bad version. more notes soon.

quick reference for 0283 move zeroes. more notes soon.

quick reference for 0290 word pattern. more notes soon.

quick reference for 0292 nim game. more notes soon.

quick reference for 0303 range sum query immutable. more notes soon.

quick reference for 0326 power of three. more notes soon.

quick reference for 0338 counting bits. more notes soon.

quick reference for 0342 power of four. more notes soon.

quick reference for 0344 reverse string. more notes soon.

quick reference for 0345 reverse vowels of a string. more notes soon.

quick reference for 0349 intersection of two arrays. more notes soon.

quick reference for 0350 intersection of two arrays ii. more notes soon.

quick reference for 0367 valid perfect square. more notes soon.

quick reference for 0374 guess number higher or lower. more notes soon.

quick reference for 0383 ransom note. more notes soon.

quick reference for 0387 first unique character in a string. more notes soon.

quick reference for 0389 find the difference. more notes soon.

quick reference for 0392 is subsequence. more notes soon.

quick reference for 0401 binary watch. more notes soon.

quick reference for 0404 sum of left leaves. more notes soon.

quick reference for 0405 convert a number to hexadecimal. more notes soon.

quick reference for 0409 longest palindrome. more notes soon.

quick reference for 0412 fizz buzz. more notes soon.

quick reference for 0414 third maximum number. more notes soon.

quick reference for 0415 add strings. more notes soon.

quick reference for 0434 number of segments in a string. more notes soon.

quick reference for 0441 arranging coins. more notes soon.

quick reference for 0448 find all numbers disappeared in an array. more notes soon.

quick reference for 0455 assign cookies. more notes soon.

quick reference for 0459 repeated substring pattern. more notes soon.

quick reference for 0461 hamming distance. more notes soon.

quick reference for 0463 island perimeter. more notes soon.

quick reference for 0476 number complement. more notes soon.

quick reference for 0482 license key formatting. more notes soon.

quick reference for 0485 max consecutive ones. more notes soon.

quick reference for 0492 construct the rectangle. more notes soon.

quick reference for 0495 teemo attacking. more notes soon.

quick reference for 0496 next greater element i. more notes soon.

quick reference for 0500 keyboard row. more notes soon.

quick reference for 0501 find mode in binary search tree. more notes soon.

quick reference for 0504 base 7. more notes soon.

quick reference for 0506 relative ranks. more notes soon.

quick reference for 0507 perfect number. more notes soon.

quick reference for 0509 fibonacci number. more notes soon.

quick reference for 0520 detect capital. more notes soon.

quick reference for 0521 longest uncommon subsequence i. more notes soon.

quick reference for 0530 minimum absolute difference in bst. more notes soon.

quick reference for 0541 reverse string ii. more notes soon.

quick reference for 0543 diameter of binary tree. more notes soon.

quick reference for 0551 student attendance record i. more notes soon.

quick reference for 0557 reverse words in a string iii. more notes soon.

quick reference for 0559 maximum depth of n ary tree. more notes soon.

quick reference for 0561 array partition. more notes soon.

quick reference for 0563 binary tree tilt. more notes soon.

quick reference for 0566 reshape the matrix. more notes soon.

quick reference for 0572 subtree of another tree. more notes soon.

quick reference for 0575 distribute candies. more notes soon.

quick reference for array with elements not equal to average of neighbors. more notes soon.

quick reference for candy. more notes soon.

quick reference for contains duplicate 3. more notes soon.

quick reference for convert sorted array to binary search tree. more notes soon.

quick reference for count of range sum. more notes soon.

quick reference for design neighbor sum service. more notes soon.

quick reference for first missing positive. more notes soon.

quick reference for largest palindrome product. more notes soon.

quick reference for largest plus sign. more notes soon.

quick reference for magic squares in grid. more notes soon.

quick reference for max points on line. more notes soon.

quick reference for maximal square. more notes soon.

quick reference for maximize area of square hole in grid. more notes soon.

quick reference for maximum sum of an hourglass. more notes soon.

quick reference for median of two sorted arrays. more notes soon.

quick reference for minimum path sum. more notes soon.

quick reference for number of digit one. more notes soon.

quick reference for palindrome pairs. more notes soon.

quick reference for regular expression matching. more notes soon.

quick reference for reverse pairs. more notes soon.

quick reference for russian doll envelopes. more notes soon.

quick reference for search a 2d matrix. more notes soon.

quick reference for set matrix zeroes. more notes soon.

quick reference for simplify path. more notes soon.

quick reference for sliding window median. more notes soon.

quick reference for stamping the grid. more notes soon.

quick reference for strong password checker. more notes soon.

quick reference for two sum. more notes soon.

quick reference for unique paths ii. more notes soon.

quick reference for valid number. more notes soon.

quick reference for wiggle sort ii. more notes soon.

quick reference for wildcard matching. more notes soon.

quick reference for word ladder. more notes soon.

quick reference for word ladder 2. more notes soon.

quick reference for zuma game. more notes soon.

find all shortest transformation sequences from beginWord to endWord using bfs with path tracking.

quick reference for insertion sort list. more notes soon.

Sliding a fixed hourglass mask through the grid and tracking the best sum with constant-time updates.

Binary search on the side length of the square holes while counting rails removed along each axis.

compress string in-place by replacing consecutive characters with character and count using two pointers.

quick reference for select data. more notes soon.

check if rectangles form exact rectangle without gaps or overlaps using corner counting and area validation.

Check every 3×3 window for the 1..9 magic square pattern using center and parity pruning.

quick reference for largest magic square. more notes soon.

determine if a frog can cross a river using dfs with memoization, tracking position and last jump distance.

match string against pattern with . and * using dynamic programming with memoization.

check if there exist two indices with value difference ≤ valueDiff and index difference ≤ indexDiff using sliding window with sorted array.

add two numbers

letter combinations of a phone number

median of two sorted arrays

17 solving leetcode problems

18 solving leetcode problems part2

overview of my leetcode writeups and plan

basic calculator

skyline problem

shortest palindrome

longest substring without repeating characters

longest palindromic substring

container with most water

3sum

remove nth node from end of list

valid parentheses

merge two sorted lists

generate parentheses

merge k sorted lists

next permutation

search in rotated sorted array

find first and last position of element in sorted array

combination sum

trapping rain water

permutations

rotate image

group anagrams

maximum subarray

48 my leetcode journey

critical connections in a network

read n characters given read4 ii call multiple times

sliding window maximum

trips and users

integer to english words

expression add operators

find median from data stream

serialize and deserialize binary tree

remove invalid parentheses

burst balloons

count of smaller numbers after self

longest increasing path in a matrix

patching array

reconstruct itinerary

self crossing

data stream as disjoint intervals

max sum of rectangle no larger than k

insert delete getrandom o1 duplicates allowed

all oone data structure

arithmetic slices ii subsequence

count pairs where nums[i] > 2 * nums[j] and i < j using merge sort with counting during merge phase.

quick reference for minimum window substring. more notes soon.

quick reference for count artifacts that can be extracted. more notes soon.

quick reference for get the size of a dataframe. more notes soon.

design a service to compute sums of adjacent and diagonal neighbors using prefix sums and linear search.

quick reference for find minimum in rotated sorted array ii. more notes soon.

count subarrays with sum in range [lower, upper] using prefix sums and merge sort counting.

match string against pattern with ? and * using dynamic programming.

find minimum sum path from top-left to bottom-right using dynamic programming with space optimization.

quick reference for sort list. more notes soon.

coordinate hydrogen and oxygen threads to form water molecules using semaphores and barrier synchronization.

quick reference for create a dataframe from list. more notes soon.

find two indices whose values sum to target using hash map for O(n) lookup.

find the smallest missing positive integer using array as hash table by placing each number at its correct index.

calculate trapped rainwater in 2d elevation map using min heap starting from boundary cells.

quick reference for sort colors. more notes soon.

quick reference for matrix block sum. more notes soon.

quick reference for root equals sum of children. more notes soon.

find maximum number of envelopes that can be nested using longest increasing subsequence on sorted envelopes.

normalize unix-style file paths by handling . and .. components using a stack.

quick reference for display the first three rows. more notes soon.

quick reference for letter cobinations of a phone number. more notes soon.