CODEWITHSUNDEEP
pythonpython-3.xlistsublist
Vinay Pratyush
Vinay Pratyush

Reputation: 11

Split my list into n sub-lists and print all possibilities

I want to divide a list into n sub-lists and print all possible sub-lists. n is integer input by user. length of list can be anything 1<=n<=len(list)

For example 
if list = [1,2,3,4]
and n=1
solution = [1,2,3,4]
if n=2
solution=([1],[2,3,4]),([1,2],[3,4]),([1,2,3],[4])
if n=3
solution=([1],[2],[3,4]),([1,2],[3],[4]),([1],[2,3],[4])

Note:- brackets do not represent tuple or any other data type output can be in any form. Ps:-This is not a code but stackoverflow forced me to format it as such This is what I tried

''''python

lst=[]
lst1=[]
lst4=[]
for i in range(0,10000):
    element=int(input())
    lst.append(element)
    print("If you want to continue adding list press y else press n")
    choice=input()
    if choice=='y':
        continue
    elif choice=='n':
        break
    else:
        print("please enter a valid choice")
print("Enter division size")
N=int(input())
maxchunk=len(lst)-N+1
for j in range(maxchunk,0,-1):
    rchunk=(len(lst)-j)//(N-1)
    lst2=lst[0:j]
    lst1.append(lst2)
    chunksize=((len(lst)-j)+1)//(N-1)
    print(chunksize)
    for k in range(j,len(lst),chunksize):
        lst3=lst[k:k+chunksize]
        lst1.append(lst3)
    lst4.append(lst1)
    lst1=[]
print(lst4)

''''

Upvotes: 0

Views: 656

Answers (2)

Jitse
Jitse

Reputation: 101

Here is an alternative approach using a recursive generator function that yields all the desired partitions for a given array and number of partitions.

def partition(arr, n):

  if n == 1:
    yield (arr,)

  else:
    for i in range(1, len(arr)):
      for other in partition(arr[i:], n-1):
        yield (arr[:i],) + other

You can call this like

for item in partition([1,2,3,4], 3):
  print(item)

Which shows

([1], [2], [3, 4])
([1], [2, 3], [4])
([1, 2], [3], [4])

Or alternatively, if you want to access everything at once

print(list(partition([1,2,3,4], 3)))

Showing

[([1], [2], [3, 4]), ([1], [2, 3], [4]), ([1, 2], [3], [4])]

Upvotes: 0

Vladimir Fokow
Vladimir Fokow

Reputation: 3883

You can use itertools.combinations to iterate over all the ways to choose n-1 split points of your list:

from itertools import combinations

lst = [10, 20, 30, 40, 50]
n = 3

result = []
# n-1 split points:
for indices in combinations(range(1, len(lst)), n-1):
    # indices are the indices of split points
    splits = []
    start = 0
    for stop in indices:
        splits.append(lst[start : stop])
        start = stop
    splits.append(lst[start : ])
    result.append(splits)

result:

[[[10], [20], [30, 40, 50]],
 [[10], [20, 30], [40, 50]],
 [[10], [20, 30, 40], [50]],
 [[10, 20], [30], [40, 50]],
 [[10, 20], [30, 40], [50]],
 [[10, 20, 30], [40], [50]]]

Upvotes: 1

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