八皇后--python代码

迭代和递归方法的运用

import random
def prettyprint(solution):      #图形化处理数据
    def line(pos,length=len(solution)):   #单行数据的处理
        return '.'*(pos) + 'x'+'.'*(length-pos-1)
    for pos in solution:       #画出每八行的图
        print line(pos)
def conflict(state,nextX):   #检测是否有冲突
    nextY = len(state)
    for i in range(nextY):
        if abs(state[i]-nextX) in (0,nextY-i):  #按照距离进行比较
            return True
    return False
 
#def queens(num,state):
#    if len(state) == num-1:
#        for pos in range(num):
#            if not conflict(state,pos):
#                yield pos

def queens(num=8,state=()):
    for pos in range(num):
        print state
        if not conflict(state,pos):
            if len(state)==num-1:         #最后一个
                yield (pos,)              #迭代方法
            else:
                for result in queens(num,state+(pos,)):   #递归前七个数据
#                    print result
                    yield(pos,)+result

print 'bahuanghou'
print list(queens(4))
#for i in list(queens(8)):
#    prettyprint(i)
#    print 'next'
#prettyprint(random.choice(list(queens(8))))