如何插入多层嵌套列表的中间？

Question

我正在尝试创建一个程序，在另一个嵌套列表的中间插入一个列表。就像一个三明治夹着另一个三明治等等。我正在尝试递归地解决这个问题，但我不知道该怎么做。

例如

layer1 = [1,2,3,4]
layer2 = [1,2,3,4,5,6]
layer3 = [1,2,3]

output = [1,2,[1,2,3,[1,2,3],4,5,6],3,4]

这是我的上下文代码

def lasagna(N,i):
  mainLayers = formLayer(i)
  midpoint = len(mainLayers) // 2
  if i == N:
    return mainLayers
  elif i < N:
    mainLayers = mainLayers.insert(midpoint, formLayer(i))
  return lasagna(N,i+1)

Answer 1

您可以使用 *args 接受任意数量的参数，然后像这样编写递归函数。

layer1 = [1,2,3,4]
layer2 = [1,2,3,4,5,6]
layer3 = [1,2,3]
layer4 = [1,2,3,4,5,6,7,8]
layer5 = [1,2,3,4]


def sandwhich(*seq):
    res = []
    if len(seq) == 1:
        return seq[0]
    res.extend(seq[0])
    res.insert(len(res) // 2, sandwhich(*seq[1:]))

    return res


output = [1,2,[1,2,3,[1,2,3],4,5,6],3,4]

print(sandwhich(layer1, layer2, layer3))
print(sandwhich(layer1, layer2, layer3, layer4, layer5))

输出

[1, 2, [1, 2, 3, [1, 2, 3], 4, 5, 6], 3, 4]
[1, 2, [1, 2, 3, [1, [1, 2, 3, 4, [1, 2, 3, 4], 5, 6, 7, 8], 2, 3], 4, 5, 6], 3, 4]

Answer 2

稍微短一点的递归解：

layer1 = [1,2,3,4]
layer2 = [1,2,3,4,5,6]
layer3 = [1,2,3]
def nest(vals):
  a, *b = vals
  return a[:len(a)//2]+([] if not b else [nest(b)]) + a[len(a)//2:]

print(nest([layer1, layer2, layer3]))

输出：

[1, 2, [1, 2, 3, [1, 2, 3], 4, 5, 6], 3, 4]

如何插入多层嵌套列表的中间？

How can I insert in the middle of a multilayered nested list?

python

recursion

list

nested-lists