4703.sagews

# -*- coding: cp936 -*-
class queens(object):
    def __init__(self,Num):
        self.Num = Num
        a,self.ans = list(range(Num)),[]
        import itertools
        for B in itertools.permutations(a):
            Flag,N = True,list(enumerate(B))
            for (x,y) in itertools.combinations(N,2):
                if abs(x[0]-y[0]) == abs(x[1]-y[1]):
                    Flag = False
                    break
            if Flag:
                self.ans.append( N )
    def __str__(self):
        return str(self.ans)

def fact(x):
    if x<=1:return x
    else: return x*fact(x-1)

import time
START = time.time()
Num = 11
print fact(Num)
A = queens(Num)
END=time.time()
print len(A.ans),END-START

362880 352 2.92183494568

import time
for i in range(4,17):
    START = time.time()
    A = queens(i)
    print i,'\t',time.time()-START,'\t',len(A.ans)

4 0.00103783607483 2 5 0.00075101852417 10 6 0.00458002090454 4 7 0.0350069999695 40 8 0.303432941437 92 9 2.94067978859 352 10 31.2748670578 724 11 367.872130156 2680