Python实现排列组合算法

import copy    #实现list的深复制

def combine(lst, l):
    result = []
    tmp = [0]*l
    length = len(lst)
    def next_num(li=0, ni=0):
        if ni == l:
            result.append(copy.copy(tmp))
            return
        for lj in range(li,length):
            tmp[ni] = lst[lj]
            next_num(lj+1, ni+1)
    next_num()
    return result

import copy
def permutation(lst,k):
result = []
length = len(lst)
tmp = [0]*k
def next_num(a,ni=0):
if ni == k:
result.append(copy.copy(tmp))
return
for lj in a:
tmp[ni] = lj
b = a[:]
b.pop(a.index(lj))
next_num(b,ni+1)
c = lst[:]
next_num(c,0)
return result