Given an unsorted array of integers, find the length of longest increasing subsequence.

Design and implement a data structure for Least Frequently Used (LFU) cache. It should support the following operations: get and put.

There are a total of n courses you have to take, labeled from 0 to n-1.

There is a new alien language which uses the latin alphabet. However, the order among letters are unknown to you. You receive a list of non-empty words from the dictionary, where words are sorted lexicographically by the rules of this new language. Derive the order of letters in this language.

Suppose you are at a party with n people (labeled from 0 to n - 1) and among them, there may exist one celebrity. The definition of a celebrity is that all the other n - 1 people know him/her but he/she does not know any of them.

add(value): Insert a value into the HashSet. contains(value) : Return whether the value exists in the HashSet or not.remove(value): Remove a value in the HashSet. If the value does not exist in the HashSet, do nothing.

put(key, value) : Insert a (key, value) pair into the HashMap. If the value already exists in the HashMap, update the value.get(key): Returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key.remove(key) : Remove the mapping for the value key if thi...

Given a sorted (in ascending order) integer array nums of n elements and a target value, write a function to search target in nums. If target exists, then return its index, otherwise return -1.

A website domain like "discuss.leetcode.com" consists of various subdomains. At the top level, we have "com", at the next level, we have "leetcode.com", and at the lowest level, "discuss.leetcode.com". When we visit a domain like "discuss.leetcode.com", we will also visit the parent domains "leet...

The expression string may contain open ( and closing parentheses ), the plus + or minus sign -, non-negative integers and empty spaces .

The expression string may contain open ( and closing parentheses ), the plus + or minus sign -, non-negative integers and empty spaces .

The expression string contains only non-negative integers, +, -, *, / operators and empty spaces . The integer division should truncate toward zero.

Given a string, your task is to count how many palindromic substrings in this string.

Given a list of directory info including directory path, and all the files with contents in this directory, you need to find out all the groups of duplicate files in the file system in terms of their paths.

Given a binary tree, you need to find the length of Longest Consecutive Path in Binary Tree.

You are given a string representing an attendance record for a student. The record only contains the following three characters:'A' : Absent.'L' : Late.'P' : Present.A student could be rewarded if his attendance record doesn't contain more than one 'A' (absent) or more than two continuous 'L' (la...

Write a function to check whether an input string is a valid IPv4 address or IPv6 address or neither.

You are given a map in form of a two-dimensional integer grid where 1 represents land and 0 represents water. Grid cells are connected horizontally/vertically (not diagonally). The grid is completely surrounded by water, and there is exactly one island (i.e., one or more connected land cells). Th...

Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.

Given a set of non-overlapping intervals, insert a new interval into the intervals (merge if necessary).

The input strings are both non-empty and contains only characters 1 or 0.

All inputs will be in lowercase.The order of your output does not matter.

Given an array of integers nums sorted in ascending order, find the starting and ending position of a given target value.

We are given a list schedule of employees, which represents the working time for each employee.

Given a list of strings words representing an English Dictionary, find the longest word in words that can be built one character at a time by other words in words. If there is more than one possible answer, return the longest word with the smallest lexicographical order.

You may assume that there is only lower case English letters in both s and t. t is potentially a very long (length ~= 500,000) string, and s is a short string (<=100).

The length after compression must always be smaller than or equal to the original array.

A shift on A consists of taking string A and moving the leftmost character to the rightmost position. For example, if A = 'abcde', then it will be 'bcdea' after one shift on A. Return True if and only if A can become B after some number of shifts on A.

Given a string S and a character C, return an array of integers representing the shortest distance from the character C in the string.

Given n processes, each process has a unique PID (process id) and its PPID (parent process id).