Given a list of words (without duplicates), please write a program that returns all concatenated words in the given list of words.A concatenated word is defined as a string that is comprised entirely of at least two shorter words in the given array.

Remember the story of Little Match Girl? By now, you know exactly what matchsticks the little match girl has, please find out a way you can make one square by using up all those matchsticks. You should not break any stick, but you can link them up, and each matchstick must be used exactly one time.

We want to use quad trees to store an N x N boolean grid. Each cell in the grid can only be true or false. The root node represents the whole grid. For each node, it will be subdivided into four children nodes until the values in the region it represents are all the same.

这里采用深度优先的思路进行解决。先将数组按照从小到大排序，再从左往右遍历数组，每个数字有两种可能，分别是选中到子数组，或者不选中。将所有的结果收纳即可获得最终的结果集。

打印结果广度优先搜索：name:v0name:v2name:v3name:v1name:v4深度优先搜索：name:v0name:v3name:v4name:v2name:v1递归深度优先搜索：name:v0name:v2name:v1name:v4name:v3打印最短路径：name:v0name:v2name:v3nam…

从深度优先遍历的角度来看，每次遇到一个包含子节点中间双链表节点，就递归的调用展开方法将其展开，并将展开的结果插入到当前节点的后面。这里需要注意双链表前节点前后指针的变更。步骤如下：

假设左上角的所有周围面积为太平洋，右下角的所有面积为大西洋。现在使用数组来表示一大片水域，其中数组的每一个位置上的元素代表某一个小水域的高度。假定水只能从高出流向低处，要求找出所有既可以流向太平洋…

假设有一只青蛙需要过河，河中会有一些石子，青蛙必须踩在石头上才算成功。石头的位置用整数数组来表示。青蛙的行走规则为：假设上一次青蛙跳了k格，则当前青蛙只能跳k-1或k或k+1格，且青蛙只能向前跳，不能向后跳。

将一个字符串解码，要求按照次数展开原字符串中的中括号。如3[a]2[bc]对应的字符串就是aaabcbc，即a展开3次，bc展开2次。注意，源字符串中的括号是允许嵌套的，且展开的字符中不会包含任何数字。

The n-queens puzzle is the problem of placing n queens on an n×n chessboard such that no two queens attack each other.