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

题目：Given a list of airline tickets represented by pairs of departure and arrival airports [from, to], reconstruct the itinerary in order. All of the tickets belong to a man who departs from JFK. Thus, the itinerary must begin with JFK.

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

题目：Given a binary tree, find the length of the longest consecutive sequence path.

题目：The thief has found himself a new place for his thievery again. There is only one entrance to this area, called the "root." Besides the root, each house has one and only one parent house. After a tour, the smart thief realized that "all houses in this place forms a binary tree". It will aut...

题目：Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file or memory buffer, or transmitted across a network connection link to be reconstructed later in the same or another computer environment.

问题：Given a binary tree, imagine yourself standing on the right side of it, return the values of the nodes you can see ordered from top to bottom.

题目：Follow up for problem "Populating Next Right Pointers in Each Node".

Note:A solution using O(n) space is pretty straight forward. Could you devise a constant space solution?

Definition of a complete binary tree from Wikipedia:In a complete binary tree every level, except possibly the last, is completely filled, and all nodes in the last level are as far left as possible. It can have between 1 and 2h nodes inclusive at the last level h.

题目：Given a binary tree, return the postorder traversal of its nodes' values.

题目：Given a binary tree, return the preorder traversal of its nodes' values.

题目：Given two integers representing the numerator and denominator of a fraction, return the fraction in string format.

题目：Given a binary tree, return the inorder traversal of its nodes' values.

问题：Given n points on a 2D plane, find if there is such a line parallel to y-axis that reflect the given points.

题目：Given a non-empty string str and an integer k, rearrange the string such that the same characters are at least distance k from each other.

题目：Given a string, we can "shift" each of its letter to its successive letter, for example: "abc" -> "bcd". We can keep "shifting" which forms the sequence:

题目：Given a string, find the length of the longest substring T that contains at most 2 distinct characters.

题目：You are playing the following Bulls and Cows game with your friend: You write down a number and ask your friend to guess what the number is. Each time your friend makes a guess, you provide a hint that indicates how many digits in said guess match your secret number exactly in both digit an...

题目：Given a 2D binary matrix filled with 0's and 1's, find the largest rectangle containing all ones and return its area.

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

问题：Given an array of integers, return indices of the two numbers such that they add up to a specific target.

For example, given: ["eat", "tea", "tan", "ate", "nat", "bat"], Return:

题目：Given an unsorted array, find the maximum difference between the successive elements in its sorted form.

题目：Given an array of citations (each citation is a non-negative integer) of a researcher, write a function to compute the researcher's h-index.

题目：Given an array with n objects colored red, white or blue, sort them so that objects of the same color are adjacent, with the colors in the order red, white and blue.

注意新的list跟原来的list是不相连的，然后把各个状态的点记录好就行： {代码...}

这道题开始想容易陷入一个误区：我要怎么比较这两个单独的数，使得它们拼起来的结果最大呢？然而如果真的仔细比较这两个数最后得出一个结论，代码会很长，楼主已经试过了。。。后来转念一想，直接比较两个数拼成的结果不就好了，长度一样，所以省去了很多麻烦。程序如下：

Bubble Sort就不说了，下面简单总结一个Selection Sort, Insertion Sort, Merge Sort和Quick Sort:

题目：Sort a linked list in O(n log n) time using constant space complexity.