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Python Counter| Find duplicate rows in a binary matrix
  • Last Updated : 30 Dec, 2020
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Given a binary matrix whose elements are only 0 and 1, we need to print the rows which are duplicate of rows which are already present in the matrix.

Examples:

Input : [[1, 1, 0, 1, 0, 1],
         [0, 0, 1, 0, 0, 1],
         [1, 0, 1, 1, 0, 0],
         [1, 1, 0, 1, 0, 1],
         [0, 0, 1, 0, 0, 1],
         [0, 0, 1, 0, 0, 1]]

Output : (1, 1, 0, 1, 0, 1)
         (0, 0, 1, 0, 0, 1)

We have existing solution for this problem please refer Find duplicate rows in a binary matrix link. We can solve this problem very quickly in Python using Counter() method. Approach is very simple,

  1. Create a dictionary using counter method which will have rows as key and it’s frequency as value.
  2. Now traverse dictionary completely and print all rows which have frequency greater than 1.




# Function to find duplicate rows in a binary matrix
from collections import Counter
  
def duplicate(input):
  
     # since lists are unhasable for counter method
     # because lists are mutable so first we will cast
     # each row (list) into tuple
     input = map(tuple,input)
  
     # now create dictionary
     freqDict = Counter(input)
  
     # print all rows having frequency greater than 1
     for (row,freq) in freqDict.items():
          if freq>1:
              print (row)
  
# Driver program
if __name__ == "__main__":
    input = [[1, 1, 0, 1, 0, 1],
            [0, 0, 1, 0, 0, 1],
            [1, 0, 1, 1, 0, 0],
            [1, 1, 0, 1, 0, 1],
            [0, 0, 1, 0, 0, 1],
            [0, 0, 1, 0, 0, 1]]
    duplicate(input)

Output:

(1, 1, 0, 1, 0, 1)
(0, 0, 1, 0, 0, 1)

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