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 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.