每日一題系列 - 全排列算法python實現

 題目：

給定整數n, 實現[1,n)的所有冪等實現, 不限順序。例如n=4

123

132

213

231

312

321

 

答案：

調用MM(n)，可以的到該排列組合的list集合。代碼如下：

def Mideng(li): if(type(li)!=list): return if(len(li)==1): return [li] result=[] for i in range(0,len(li[:])): bak=li[:] head=bak.pop(i) #head of the recursive-produced value for j in Mideng(bak): j.insert(0,head) result.append(j) return result def MM(n): if(type(n)!=int or n<2): return return Mideng(list(range(1,n)))

 

 

測試：

 

-->MM(6)

 

[[1, 2, 3, 4, 5], [1, 2, 3, 5, 4], [1, 2, 4, 3, 5], [1, 2, 4, 5, 3], [1, 2, 5, 3, 4], [1, 2, 5, 4, 3], [1, 3, 2, 4, 5], [1, 3, 2, 5, 4], [1, 3, 4, 2, 5], [1, 3, 4, 5, 2], [1, 3, 5, 2, 4], [1, 3, 5, 4, 2], [1, 4, 2, 3, 5], [1, 4, 2, 5, 3], [1, 4, 3, 2, 5], [1, 4, 3, 5, 2], [1, 4, 5, 2, 3], [1, 4, 5, 3, 2], [1, 5, 2, 3, 4], [1, 5, 2, 4, 3], [1, 5, 3, 2, 4], [1, 5, 3, 4, 2], [1, 5, 4, 2, 3], [1, 5, 4, 3, 2], [2, 1, 3, 4, 5], [2, 1, 3, 5, 4], [2, 1, 4, 3, 5], [2, 1, 4, 5, 3], [2, 1, 5, 3, 4], [2, 1, 5, 4, 3], [2, 3, 1, 4, 5], [2, 3, 1, 5, 4], [2, 3, 4, 1, 5], [2, 3, 4, 5, 1], [2, 3, 5, 1, 4], [2, 3, 5, 4, 1], [2, 4, 1, 3, 5], [2, 4, 1, 5, 3], [2, 4, 3, 1, 5], [2, 4, 3, 5, 1], [2, 4, 5, 1, 3], [2, 4, 5, 3, 1], [2, 5, 1, 3, 4], [2, 5, 1, 4, 3], [2, 5, 3, 1, 4], [2, 5, 3, 4, 1], [2, 5, 4, 1, 3], [2, 5, 4, 3, 1], [3, 1, 2, 4, 5], [3, 1, 2, 5, 4], [3, 1, 4, 2, 5], [3, 1, 4, 5, 2], [3, 1, 5, 2, 4], [3, 1, 5, 4, 2], [3, 2, 1, 4, 5], [3, 2, 1, 5, 4], [3, 2, 4, 1, 5], [3, 2, 4, 5, 1], [3, 2, 5, 1, 4], [3, 2, 5, 4, 1], [3, 4, 1, 2, 5], [3, 4, 1, 5, 2], [3, 4, 2, 1, 5], [3, 4, 2, 5, 1], [3, 4, 5, 1, 2], [3, 4, 5, 2, 1], [3, 5, 1, 2, 4], [3, 5, 1, 4, 2], [3, 5, 2, 1, 4], [3, 5, 2, 4, 1], [3, 5, 4, 1, 2], [3, 5, 4, 2, 1], [4, 1, 2, 3, 5], [4, 1, 2, 5, 3], [4, 1, 3, 2, 5], [4, 1, 3, 5, 2], [4, 1, 5, 2, 3], [4, 1, 5, 3, 2], [4, 2, 1, 3, 5], [4, 2, 1, 5, 3], [4, 2, 3, 1, 5], [4, 2, 3, 5, 1], [4, 2, 5, 1, 3], [4, 2, 5, 3, 1], [4, 3, 1, 2, 5], [4, 3, 1, 5, 2], [4, 3, 2, 1, 5], [4, 3, 2, 5, 1], [4, 3, 5, 1, 2], [4, 3, 5, 2, 1], [4, 5, 1, 2, 3], [4, 5, 1, 3, 2], [4, 5, 2, 1, 3], [4, 5, 2, 3, 1], [4, 5, 3, 1, 2], [4, 5, 3, 2, 1], [5, 1, 2, 3, 4], [5, 1, 2, 4, 3], [5, 1, 3, 2, 4], [5, 1, 3, 4, 2], [5, 1, 4, 2, 3], [5, 1, 4, 3, 2], [5, 2, 1, 3, 4], [5, 2, 1, 4, 3], [5, 2, 3, 1, 4], [5, 2, 3, 4, 1], [5, 2, 4, 1, 3], [5, 2, 4, 3, 1], [5, 3, 1, 2, 4], [5, 3, 1, 4, 2], [5, 3, 2, 1, 4], [5, 3, 2, 4, 1], [5, 3, 4, 1, 2], [5, 3, 4, 2, 1], [5, 4, 1, 2, 3], [5, 4, 1, 3, 2], [5, 4, 2, 1, 3], [5, 4, 2, 3, 1], [5, 4, 3, 1, 2], [5, 4, 3, 2, 1]]

 

實際上,該序列是個全排列，所以總共數目是1x2x3...x(n-1)=(n-1)!

-->len(MM(6))=120

正確