160.Intersection of Two Linked Lists
Given the heads of two singly linked-lists and , return the node at which the two lists intersect. If the two linked lists have no intersection at all, return .
For example, the following two linked lists begin to intersect at node :
145.Binary Tree Postorder Traversal
Given the of a binary tree, return the postorder traversal of its nodes’ values.
Example 1:
144.Binary Tree Preorder Traversal
Given the of a binary tree, return the preorder traversal of its nodes’ values.
Example 1:
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 following the next pointer. Internally, is used to denote the index of the node that tail’s next pointer is connected to. Note that is not passed as a parameter.
Given a non-empty array of integers , every element appears twice except for one. Find that single one.
You must implement a solution with a linear runtime complexity and use only constant extra space.
125.Valid Palindrome
A phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the same forward and backward. Alphanumeric characters include letters and numbers.
Given a string , return if it is a palindrome, or otherwise.
Example 1:
121.Best Time to Buy and Sell Stock
You are given an array where is the price of a given stock on the day.
You want to maximize your profit by choosing a single day to buy one stock and choosing a different day in the future to sell that stock.
Given an integer , return the (0-indexed) row of the Pascal’s triangle.
In Pascal’s triangle, each number is the sum of the two numbers directly above it as shown:
Given an integer , return the first of Pascal’s triangle.
In Pascal’s triangle, each number is the sum of the two numbers directly above it as shown: