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Python | Remove sublists that are present in another sublist
  • Difficulty Level : Medium
  • Last Updated : 08 Apr, 2019
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Given a list of lists, write a Python program to remove sublists from the given list of lists that are present in another sublist.

Examples:

Input : [['a', 'b', 'c'], ['a', 'c'], ['a', 'b', 'c'], ['d']]
Output : [['a', 'b', 'c'], ['d']]

Input : [[1], [1, 2], [1, 2, 3], [0], [0, 1]]
Output : [[1, 2, 3], [0, 1]]

 
Approach #1 : Using Python Set (If order of list doesn’t matter)

This approach makes use of Python sets. Create two empty lists ‘curr_res’ to store current sublist and ‘result’ to store the finalized sublists. Convert the sub-lists in the given list of lists to sets and sort them by length in reverse order, so that you can iterate through them and add each set to the curr_res only if it is not a subset of any of the existing sets in the curr_res.
The only drawback of this approach is that it may produce the result in an unordered way(Since sets are unordered).




# Python3 program to remove sublists from
# list of lists that are in another sublist
  
def removeSublist(lst):
    curr_res = []
    result = []
    for ele in sorted(map(set, lst), key = len, reverse = True):
        if not any(ele <= req for req in curr_res):
            curr_res.append(ele)
            result.append(list(ele))
          
    return result
      
# Driver code
lst = [['a', 'b', 'c'], ['a', 'b'], ['a', 'b', 'c'], ['d']]
print(removeSublist(lst))
Output:



[['c', 'b', 'a'], ['d']]

 
Approach #2 : Using Python Dictionary (If order of list matters)

Dict may not always produce ordered output, therefore you can use OrderedDict from collections module.




# Python3 program to remove sublists from
# list of lists that are in another sublist
from collections import OrderedDict
  
def removeSublist(lst):
    curr_result = []
    result = []
    for ele in sorted(map(OrderedDict.fromkeys, lst), key = len, reverse = True):
        if not any(ele.keys() <= req.keys() for req in curr_result):
            curr_result.append(ele)
            result.append(list(ele))
              
    return result
      
# Driver code
lst = [['a', 'b', 'c'], ['a', 'b'], ['a', 'b', 'c'], ['d']]
print(removeSublist(lst))
Output:
[['a', 'b', 'c'], ['d']]

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