N皇后问题

题目描述：

在N*N的方格棋盘放置了N个皇后，使得它们不相互攻击（即任意2个皇后不允许处在同一排，同一列，也不允许处在与棋盘边框成45角的斜线上。

你的任务是，对于给定的N，求出有多少种合法的放置方法。

输入：

共有若干测试用例，每个测试用例对应一行一个正整数N≤10，表示棋盘和皇后的数量；如果N=0，表示输入结束。

输出：

对每个测试用例输出一行一个正整数，表示对应棋盘的皇后的可行放置方案总数。-N queens problem

Subject descr iption:

In the N* N of checkerboard placed N queens so that they do not attack each other (that is, any two Queens are not allowed in the same row, the same column, are not allowed on the board at a 45 angle diagonal border .

Your task is, for a given N, determine how many legitimate way of placing.

enter:

There are a number of test cases, each test case corresponds to a row of a positive integer N≤10, represents the board number and queens　if N = 0, indicates the end of input.

Output:

For each test case output a line a positive integer representing the total number of viable placement program corresponding to the board of the Queen.