recursion

Add Two Numbers

Add Two Numbers requires careful linked-list pointer manipulation to sum digits while handling carries efficiently in in…

Regular Expression Matching

The Regular Expression Matching problem involves checking if a string matches a pattern using '.' and '*'.

Merge Two Sorted Lists

Merge two sorted linked lists by splicing nodes into one sorted list using linked-list pointer manipulation and recursio…

Swap Nodes in Pairs

Learn how to swap every adjacent linked-list pair by rewiring nodes safely without changing values or breaking the remai…

Reverse Nodes in k-Group

Reverse Nodes in k-Group challenges you to reverse segments of a linked list in groups of size k.

Wildcard Matching

Implement full wildcard pattern matching using '?' and '*' by applying state transition dynamic programming with careful…

Pow(x, n)

Calculate x to the power n efficiently using recursion and exponentiation, handling negative powers and large inputs saf…

Permutation Sequence

Find the kth permutation sequence of a set of numbers using math and recursion to efficiently compute the result.

Reorder List

Reorder List requires careful pointer manipulation in a singly linked list to interleave nodes from the ends without alt…

Remove Linked List Elements

Remove all nodes from a linked list that have a specific value, adjusting pointers to preserve the rest of the list.

Reverse Linked List

Reverse a singly linked list in place, converting the head to tail, with an iterative or recursive approach.

Basic Calculator

Implement a basic calculator to evaluate mathematical expressions, ensuring correct evaluation with stack-based manageme…

Power of Two

Determine if a given integer is a power of two using efficient math and bit manipulation techniques with optional recurs…

Number of Digit One

Compute the total number of digit one appearing in all numbers from 0 up to n using state transition dynamic programming…

Palindrome Linked List

Solve Palindrome Linked List by finding the midpoint, reversing the second half, and comparing mirrored nodes in linear …

Different Ways to Add Parentheses

Solve Different Ways to Add Parentheses by splitting on each operator and memoizing every subexpression result list.

Integer to English Words

Convert a given integer to its English words representation using mathematical logic and string manipulation.

Power of Three

Determine if a given integer is a power of three using math and recursion techniques.

Power of Four

Determine if a given integer is a power of four using math insights and bit manipulation tricks efficiently in code.

Elimination Game

Elimination Game uses a systematic removal of numbers with alternating left-right passes, solvable with math and recursi…

Decode String

Decode a nested encoded string using stack-based state management, handling repeated patterns efficiently with recursion…

Predict the Winner

Predict the Winner involves two players taking turns to maximize their score by picking from either end of an array, opt…

Fibonacci Number

Calculate the nth Fibonacci number using state transition dynamic programming and recursive techniques efficiently in in…

Parse Lisp Expression

Parse Lisp expressions using stack-based state management to evaluate variables and operations.