给定一个数组，找出其所有可能的排列。
import numpy as np
def permutations(arr):if len(arr)<=1:return([arr])t = [arr[0:1]]i = 1while i<=len(arr)-1:a = arr[i]t = [xs[0:j]+[a]+xs[j:] for xs in t for j in range(i+1)]t = np.unique(t,axis=0).tolist()i = i+1return(t)print(permutations([1,1,3]))