Python学习笔记60

八皇后问题 （循环递归法）

#* queen problem with recurison

BOARD_SIZE =8

def under_attack(col, queens):

  left = right = col

  for r, c in reversed(queens):

#左右有冲突的位置的列号

      left, right = left -1, right +1

      if c in(left, col, right):

          returnTrue

  returnFalse

def solve(n):

  if n ==0:

      return[[]]

  smaller_solutions = solve(n -1)

  return[solution+[(n,i+1)]

      for i in xrange(BOARD_SIZE)

          for solution in smaller_solutions

              ifnot under_attack(i+1, solution)]

for answer in solve(BOARD_SIZE):

  print answer