用递归实现的全排列生成器如下:
num = [str(i) for i in xrange(10)]
def perm(num,s):
if s==len(num):
yield ''.join(num)
for i in xrange(s,len(num)):
num[s],num[i] = num[i],num[s]
perm(num,s+1)
num[s],num[i] = num[i],num[s]
f=perm(num,0)
print f.next()
运行后提示如下:
Traceback (most recent call last):
File "###",line 10,in <module>
f.next()
StopIteration
我自己检查,发现递归根本进不去啊,是不是我使用yield的方法不对啊?
def perm(num,s):
if s==len(num):
yield ''.join(num)
for i in xrange(s,len(num)):
num[s],num[i] = num[i],num[s]
for each in perm(num,s+1):
yield each
num[s],num[i] = num[i],num[s]