Rosalind第19题——ros_bio19_PERM_bio19降维-优快云博客

本文链接：https://blog.youkuaiyun.com/qq_45380519/article/details/119361250

本文介绍了使用递归方法和Python内置模块实现排列算法的过程。通过递归函数和itertools.permutations方法展示了不同实现方式，并提供了一种额外的排列算法实现。

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#递归果然还是不太会用！！

def permutation(li):
    len_list = len(li)
    if len_list == 1:
        return li

    result = []
    for i in range(len_list):
        res_list = li[:i] + li[i + 1:]
        s = li[i]
        per_result = permutation(res_list)
        if len(per_result) == 1:
            result.append([s] + per_result)
        else:
            result += [[s] + j for j in per_result]
    return result


n = int(input('请输入n：'))
a = []
while n > 0:
    a.append(n)
    n -= 1
per = permutation(a[::-1])
print(len(per))
s = ''
for i in per:
    n = [str(x) for x in i]
    s = ' '.join(n)
    print(s)


'''
#python自带的模块
import itertools


def permutation(li):
    return list(itertools.permutations(li))


n = int(input('请输入n：'))
a = []
while n > 0:
    a.append(n)
    n -= 1

per = permutation(a[::-1])
print(per)
'''


'''
#另一种做法
def perm(seq, begin, end):
#进行排列的函数
    global num
    if begin == end:
        print(" ".join(seq))
        num += 1
    else:
        for index in range(begin, end):
            seq[index], seq[begin] = seq[begin], seq[index]
            perm(seq, begin + 1, end)
            seq[index], seq[begin] = seq[begin], seq[index]


num = 0
seq = ['1', '2', '3']
perm(seq, 0, len(seq))
print(num)
#作者：未琢 https://www.bilibili.com/read/cv2077119 出处：bilibili
'''