class Solution(object):
def totalNQueens(self, n):
"""
:type n: int
:rtype:
"""
self.col = [False for i in range(n)]
self.diaS = [False for i in range(2 * n - 1)]
self.diaN = [False for i in range(2 * n - 1)]
ans = []
self.res = 0
self.putQueen(n, 0, ans)
print self.res
# 尝试在一个n皇后的问题中，摆放第index行皇后的位置
def putQueen(self, n, index, ans):
if index == n:
self.res += 1
# self.res.append(ans[0:])
return
# 尝试将第index行的皇后摆放在第i列
for i in range(n):
if not self.col[i] and not self.diaS[index + i] and not self.diaN[index - i + n - 1]:
ans.append(i)
self.col[i] = True
self.diaS[index + i] = True
self.diaN[index - i + n - 1] = True
self.putQueen(n, index + 1, ans)
ans.pop()
self.col[i] = False
self.diaS[index + i] = False
self.diaN[index - i + n - 1] = False
return
