n皇后问题可以表示成n-元组(x1,…,xn),其中xi是放在第i行的皇后所在的列号。于是，解空间由nn个n-元组组成。

显示约束条件为Si={1,2,…….,n},1 i  n。

隐式约束条件之一为没有两个xi相同(即任意两个皇后不在同一列上)。将其加入到显式条件中，于是解空间的大小由nn个元组减少到n！个元组。

-n queens problem can be expressed as n-tuple (x1, ..., xn), where xi is the queen on the first i rows where the column number. As a result, the solution space by the nn a n-tuple integral. Shows the constraints for the Si = (1,2, ... ...., N), 1 　i 　n. One of the implicit constraint that no two xi the same (ie any two Queen' s not in the same column). Be added to the explicit conditions, so the solution space the size of a tuple from nn reduced to n! A tuple.