# Problemrosalind練習(xí)題十八

# A permutation of length n is an ordering of the positive integers {1,2,…,n}. For example, π=(5,3,2,1,4) is a permutation of length 5.

# Given: A positive integer n≤7.

# Return: The total number of permutations of length n, followed by a list of all such permutations (in any order).

# Sample Dataset

# 3

# Sample Output

# 6

# 1 2 3

# 1 3 2

# 2 1 3

# 2 3 1

# 3 1 2

# 3 2 1

# 這個(gè)題目的目的是輸出長(zhǎng)度為n的排列的個(gè)數(shù)以及所有排列。

import itertools

n = 3 # 讀取輸入n

perms = list(itertools.permutations(range(1, n+1))) # 求出所有排列

print(len(perms)) # 輸出排列個(gè)數(shù)

for perm in perms: # 輸出每個(gè)排列

? ? print(" ".join(str(x) for x in perm))