hash table

Longest Substring Without Repeating Characters

Find the length of the longest substring without repeating characters using a sliding window and hash map to track state…

Integer to Roman

Convert a given integer to its Roman numeral representation using hash table mapping and decimal place math operations e…

Roman to Integer

Convert a Roman numeral string into an integer using a hash table and mathematical principles to determine value order.

Letter Combinations of a Phone Number

Generate all letter combinations a digit string can represent using backtracking with pruning, leveraging hash table map…

Substring with Concatenation of All Words

Find all starting indices of substrings in a string that are concatenations of a given list of words.

Valid Sudoku

Check if a 9x9 Sudoku board is valid by scanning rows, columns, and sub-boxes with hash lookups, ensuring no duplicates …

Sudoku Solver

Solve the Sudoku puzzle by filling empty cells while respecting Sudoku's rules using array scanning and backtracking.

First Missing Positive

Identify the smallest missing positive integer in an unsorted array using constant space and linear time scanning techni…

Group Anagrams

Group the anagrams in a list of strings using efficient hash table-based methods, focusing on array scanning.

Set Matrix Zeroes

Modify the matrix in place by setting rows and columns to zero when an element is zero.

Minimum Window Substring

Find the smallest substring of s containing all characters from t using a sliding window with running state updates for …

Construct Binary Tree from Preorder and Inorder Traversal

Construct a binary tree using preorder and inorder traversal arrays, leveraging array scanning and hash table lookups.

Construct Binary Tree from Inorder and Postorder Traversal

Reconstruct a binary tree from given inorder and postorder arrays using array scanning and hash lookup to optimize recur…

Word Ladder II

Find all shortest transformation sequences from beginWord to endWord using a dictionary, leveraging backtracking search …

Word Ladder

Find the shortest transformation sequence from a start word to an end word, with each word in the sequence differing by …

Longest Consecutive Sequence

Find the length of the longest consecutive elements sequence in an unsorted array using array scanning and hash lookup.

Clone Graph

Clone Graph involves cloning a graph using DFS, focusing on graph traversal and neighbor management using hash tables.

Copy List with Random Pointer

This problem requires copying a linked list where each node has a random pointer in addition to the next pointer.

Word Break

Determine if a string can be fully segmented into dictionary words using array scanning and hash-based lookups for effic…

Word Break II

Given a string and dictionary, return all possible sentences by adding spaces where each word is in the dictionary.

Linked List Cycle

Determine if a given linked list contains a cycle using pointer manipulation or hashing, focusing on detecting repeated …

Linked List Cycle II

Identify the start of a cycle in a linked list using pointer manipulation, efficiently handling edge cases without modif…

LRU Cache

Implement an efficient LRU Cache using hash table and doubly-linked list to achieve O(1) operations for get and put.

Max Points on a Line

Find the maximum number of points on a straight line in a 2D plane using array scanning and hash lookup.