我刚刚解决了

python中的nqueen问题.该解决方案输出了将n个皇后放置在nXn棋盘上的解决方案总数,但尝试使用n = 15需要一个多小时才能得到答案.任何人都可以看看代码,并给我提示加快这个程序……一个新手python程序员.

#!/usr/bin/env python2.7

##############################################################################

# a script to solve the n queen problem in which n queens are to be placed on

# an nxn chess board in a way that none of the n queens is in check by any other

#queen using backtracking'''

##############################################################################

import sys

import time

import array

solution_count = 0

def queen(current_row, num_row, solution_list):

if current_row == num_row:

global solution_count

solution_count = solution_count + 1

else:

current_row += 1

next_moves = gen_nextpos(current_row, solution_list, num_row + 1)

if next_moves:

for move in next_moves:

'''make a move on first legal move of next moves'''

solution_list[current_row] = move

queen(current_row, num_row, solution_list)

'''undo move made'''

solution_list[current_row] = 0

else:

return None

def gen_nextpos(a_row, solution_list, arr_size):

'''function that takes a chess row number, a list of partially completed

placements and the number of rows of the chessboard. It returns a list of

columns in the row which are not under attack from any previously placed

queen.

'''

cand_moves = []

'''check for each column of a_row which is not in check from a previously

placed queen'''

for column in range(1, arr_size):

under_attack = False

for row in range(1, a_row):

'''

solution_list holds the column index for each row of which a

queen has been placed and using the fact that the slope of

diagonals to which a previously placed queen can get to is 1 and

that the vertical positions to which a queen can get to have same

column index, a position is checked for any threating queen

'''

if (abs(a_row - row) == abs(column - solution_list[row])

or solution_list[row] == column):

under_attack = True

break

if not under_attack:

cand_moves.append(column)

return cand_moves

def main():

'''

main is the application which sets up the program for running. It takes an

integer input,N, from the user representing the size of the chessboard and

passes as input,0, N representing the chess board size and a solution list to

hold solutions as they are created.It outputs the number of ways N queens

can be placed on a board of size NxN.

'''

#board_size = [int(x) for x in sys.stdin.readline().split()]

board_size = [15]

board_size = board_size[0]

solution_list = array.array('i', [0]* (board_size + 1))

#solution_list = [0]* (board_size + 1)

queen(0, board_size, solution_list)

print(solution_count)

if __name__ == '__main__':

start_time = time.time()

main()

print(time.time()