A robot is located at the top-left corner of a m x n grid (marked ‘Start’ in the diagram below). The robot can only move either down or right at any point in time. The robot is trying to reach the bottom-right corner of the grid (marked ‘Finish’ in the diagram below). Now consider if some obstacles are added to the grids. How many unique paths would there be?
（不同的路径II，只能向右或者向下移动在有路障的情况下从左上角移动到右下角的路径个数）
A robot is located at the top-left corner of a m x n grid (marked ‘Start’ in the diagram below). The robot can only move either down or right at any point in time. The robot is trying to reach the bottom-right corner of the grid (marked ‘Finish’ in the diagram below). How many possible unique paths are there?
（不同的路径，只能向右或者向下移动从左上角移动到右下角的路径个数）
Given a linked list, rotate the list to the right by k places, where k is non-negative.
(k 次旋转链表)
The set [1,2,3,…,n] contains a total of n! unique permutations. By listing and labeling all of the permutations in order, we get the following sequence for n = 3: “123”, “132”, “213”, “231”, “312”, “321”. Given n and k, return the k_th permutation sequence.
(排列组合结果的第 K 项)
Given a positive integer n, generate a square matrix filled with elements from 1 to n^2 in spiral order.
（螺旋式生成矩阵）
Given a string s consists of upper/lower-case alphabets and empty space characters “ ”, return the length of last word in the string. If the last word does not exist, return 0.
（字符串最后一个单词的长度）
Given a set of non-overlapping intervals, insert a new interval into the intervals (merge if necessary). You may assume that the intervals were initially sorted according to their start times.
（插入间隔区间）
Given a collection of intervals, merge all overlapping intervals.
(合并间隔区间)
Given an array of non-negative integers, you are initially positioned at the first index of the array. Each element in the array represents your maximum jump length at that position. Determine if you are able to reach the last index.
(跳棋游戏，确定能否到达队尾)
Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.
（螺旋式遍历矩阵）