Given the root of a binary tree, return its maximum depth. A binary tree’s maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node. Example 1:Inpu

Given the root of a binary tree, return the preorder traversal of its nodes’ values. Example 1:Input: root = [1,null,2,3]Output: [1,2,3] Example 2:Input: root = []Output: [] Example 3:Input:

Given a string s consisting of words and spaces, return the length of the last word in the string. A word is a maximal substring consisting of non-space characters only. Example 1:Input: s = “Hel

You are given the head of a singly linked-list. The list can be represented as:L0 → L1 → … → Ln - 1 → Ln Reorder the list to be on the following form:L0 → Ln → L1 → Ln - 1 → L2 → Ln - 2 → …You may not

You are given the heads of two sorted linked lists list1 and list2. Merge the two lists into one sorted list. The list should be made by splicing together the nodes of the first two lists. Return the

Given the head of a linked list, return the node where the cycle begins. If there is no cycle, return null. There is a cycle in a linked list if there is some node in the list that can be reached agai

Given head, the head of a linked list, determine if the linked list has a cycle in it. There is a cycle in a linked list if there is some node in the list that can be reached again by continuously fol

Given the head of a linked list, remove the nth node from the end of the list and return its head. Example 1:Input: head = [1,2,3,4,5], n = 2Output: [1,2,3,5] Example 2:Input: head = [1

Given the head of a linked list, rotate the list to the right by k places. Example 1:Input: head = [1,2,3,4,5], k = 2Output: [4,5,1,2,3] Example 2:Input: head = [0,1,2], k = 4Outpu

A peak element is an element that is strictly greater than its neighbors. Given a 0-indexed integer array nums, find a peak element, and return its index. If the array contains multiple peaks, return