Python實現排列組合算法

實現組合算法C(n,k)，可以用遞歸實現：

python代碼：

import copy    #實現list的深復制

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

 

實現排列算法A(n,k)，用遞歸實現：

k=len(lst)s時，為全排列

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