counting

Majority Element

Find the majority element in an array, where the element appears more than n/2 times, using efficient algorithms.

Majority Element II

Identify all elements in an integer array appearing more than ⌊ n/3 ⌋ times using efficient array scanning and hash coun…

Bulls and Cows

Solve the Bulls and Cows problem using hash tables and string manipulation to track exact and misplaced digits.

Top K Frequent Elements

Find the k most frequent elements from an array using efficient algorithms like hashing and sorting.

Ransom Note

Determine if a ransom note can be constructed from a magazine's letters using hash tables and string counting techniques…

First Unique Character in a String

Find the index of the first non-repeating character in a string using efficient queue-driven state processing.

Sort Characters By Frequency

Sort Characters By Frequency requires counting characters efficiently and rearranging a string in descending frequency o…

Longest Harmonious Subsequence

Find the length of the longest harmonious subsequence in an integer array using array scanning and hash-based frequency …

Task Scheduler

Task Scheduler is solved by counting task frequencies and computing how cooldown gaps force idle slots around the most f…

Top K Frequent Words

Solve Top K Frequent Words by counting each word, then ordering ties alphabetically so frequency wins before lexicograph…

Reorganize String

Reorganize a string so that no two adjacent characters are the same, if possible, using a greedy approach.

Subdomain Visit Count

The Subdomain Visit Count problem requires counting the visits to all subdomains of a given domain from a list of count-…

Most Common Word

Find the most frequent non-banned word in a paragraph, excluding punctuation, using an efficient array scan and hash tab…

Reordered Power of 2

Determine if a number's digits can be rearranged to form a power of two using counting and hash-based checks.

Uncommon Words from Two Sentences

Find uncommon words from two sentences by counting word frequencies using hash tables.

RLE Iterator

Design an efficient iterator for a run-length encoded array, handling large counts and sequential access correctly every…

X of a Kind in a Deck of Cards

Solve the problem of determining if a deck can be partitioned into groups with equal occurrences of card values.

3Sum With Multiplicity

Count all unique triplets in an integer array whose sum equals the target, handling multiplicity efficiently using hashi…

Minimum Increment to Make Array Unique

This problem challenges you to find the minimum moves to make all elements in an array unique by incrementing elements.

Subarrays with K Different Integers

Find subarrays with exactly k distinct integers in an integer array using sliding window and hash lookup techniques.

Pairs of Songs With Total Durations Divisible by 60

Calculate the number of song pairs whose total durations sum to a multiple of 60 using array scanning and hash lookups.

Distant Barcodes

Rearrange barcodes in an array so that no two adjacent elements are equal, using a greedy approach and hash table for ef…

Letter Tile Possibilities

Compute all unique non-empty sequences from given letter tiles using backtracking search with pruning efficiently.

Largest Values From Labels

Maximize the sum of selected item values while respecting label use limits using array scanning and hash tracking.