Given a non-empty, singly linked list with head node head, return a middle node of linked list.

Given an array A of non-negative integers, return an array consisting of all the even elements of A, followed by all the odd elements of A.

Given a binary array, find the maximum number of consecutive 1s in this array if you can flip at most one 0.

A string S of lowercase letters is given. We want to partition this string into as many parts as possible so that each letter appears in at most one part, and return a list of integers representing the size of these parts.

Given a string s , find the length of the longest substring t that contains at most 2 distinct characters.

Given strings S and T, find the minimum (contiguous) substring W of S, so that T is a subsequence of W.

Given a linked list and a value x, partition it such that all nodes less than x come before nodes greater than or equal to x.

Return the length of the shortest, non-empty, contiguous subarray of A with sum at least K.

Given an array of n positive integers and a positive integer s, find the minimal length of a contiguous subarray of which the sum ≥ s. If there isn't one, return 0 instead.

You are given an array of positive and negative integers. If a number n at an index is positive, then move forward n steps. Conversely, if it's negative (-n), move backward n steps. Assume the first element of the array is forward next to the last element, and the last element is backward next to...

Given a non-empty string s and an abbreviation abbr, return whether the string matches with the given abbreviation.

Given a singly linked list where elements are sorted in ascending order, convert it to a height balanced BST.

Given a string S, return the "reversed" string where all characters that are not a letter stay in the same place, and all letters reverse their positions.

In a row of seats, 1 represents a person sitting in that seat, and 0 represents that the seat is empty.

You start at any tree of your choice, then repeatedly perform the following steps:

Given two strings s1 and s2, write a function to return true if s2 contains the permutation of s1. In other words, one of the first string's permutations is the substring of the second string.Example 1:

Given a string and a string dictionary, find the longest string in the dictionary that can be formed by deleting some characters of the given string. If there are more than one possible results, return the longest word with the smallest lexicographical order. If there is no possible result, retur...

You have k lists of sorted integers in ascending order. Find the smallest range that includes at least one number from each of the k lists.

Given an array consists of non-negative integers, your task is to count the number of triplets chosen from the array that can make triangles if we take them as side lengths of a triangle.Example 1:Input: [2,2,3,4]Output: 3Explanation:Valid combinations are: 2,3,4 (using the first 2)2,3,4 (using t...

Given a string, find the length of the longest substring without repeating characters.

Returns the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.

Given an array of integers, find two numbers such that they add up to a specific target number.

Each element in the result must be unique.The result can be in any order.

Given a string, find the length of the longest substring without repeating characters.

Write a function that takes a string as input and reverse only the vowels of a string.

Given an array nums, write a function to move all 0's to the end of it while maintaining the relative order of the non-zero elements.

Given a string source and a string target, find the minimum window in source which will contain all the characters in target.

Given an array S of n integers, are there elements a, b, c, and d in S such that a + b + c + d = target?

Given an array S of n integers, find three integers in S such that the sum is closest to a given number, target. Return the sum of the three integers.

Given a linked list and a value x, partition it such that all nodes less than x come before nodes greater than or equal to x.