如何随时交换列表中的项目? [英] How to swap items in the list at any point?

问题描述

l = [ 1 ,2 ,3, 4,
      5 ,6 , 7,8,

      9,10,11,12,
      13,14,15,16,

      17,18,19,20,
      21,22,23,24
     ]

与下一行交换时在中间进行. 预期的输出:

When swapping with next line is done at the middle. Intended Output:

l = [     1 ,2 ,7,8,
          5 ,6 ,3,4,

          9,10,15,16,
          13,14,11,12,

          17,18,23,24,
          21,22,19,20
         ]

工作代码:

n = len(l) #length of list
c = 4 # column length
h =int(c/2)  #middle crossover point 

for i in range(int(c/2) , n+1, int(2*c) ):
    l[i:i+h], l[i+c:i+(c+h)] = l[i+c:i+(c+h)],l[i:i+h]
print (l)

现在，我的代码仅在交叉点位于中间时才有效.我想将其缩放到任何交叉点.我怎么做 ?对于前.如果交叉点是2nd element，则输出应为:

Now my code works only when crossover point is middle. I want to scale it to any crossover point . How do I do that ? For ex. if the crossover point is 2nd element , output should be:

l = [ 1 ,6,7,8,
      5 ,2,3,4,

      9,14,15,16,
      13,10,11,12,

      17,22,23,24,
      21,18,19,20
     ]

还请注意，列的长度可以是任何长度，在此示例中为4.

Also note that the length of column can be anything , in this example it is 4.

推荐答案

在此处使用嵌入式交换.不对所有条件进行测试.

Use in-line swap here. No test for all conditions.

def swap(lst, offset, distance, items):
    for i in range(offset, len(lst)-distance-items+1, 2*distance):
        lst[i:i+items], lst[i+distance:i+distance+items] = (
            lst[i+distance:i+distance+items], lst[i:i+items])

lst = [i+1 for i in range(24)]

swap(lst, 1, 6, 5)  # column offset:1, row length:6, item:5 to swap in-line

[ 1,  8,  9, 10, 11, 12,
     -------swap--------
  7,  2,  3,  4,  5,  6,
 13, 20, 21, 22, 23, 24,
     -------swap--------
 19, 14, 15, 16, 17, 18]

: Parameters
  lst - list to swap elements
  offset - the start index of elements to swap
  distance - the distance between each start index of elements to swap, you can think it is same as width of total columns.
  items - the number of continue elements to swap
: Return
  None, in-line swap

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