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Python program to find number of likes and dislikes

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Alice and Bob made a list of topics and both of them voted if they like or dislike the topic. They wrote 0 to denote dislike and 1 to denote like. The task is to count the number of topics that both of them like or dislike. Examples:

Input: alice = “010101” bob = “101101” Output: 3 alice and bob both like 4th and 6th topics and dislike the 5th topic. Hence, the output is 3. Input: alice = “111111” bob = “000000” Output: 0 There are no common likes or dislikes between alice and bob. Hence, the output is 0.

Input: alice = “110000” bob = “110011” Output: 4 alice and bob both like 1st and 2nd topics and dislike 3rd and 4th topics. Hence, the result is 4.


  • First, we have to iterate through each character of the string consisting of the likes and dislikes of alice.
  • Then, we have to compare it with the corresponding entry of the string consisting of the likes and dislikes of bob.
  • Finally, we will count the number of similar entries and print.

Below is the implementation. 


# function to obtain no
# of topics both alice and
# bob like
def commontopics(alice, bob):
 # initiate count with 0
 count = 0
 # iterating through alice
 for i in range(0,len(alice)):
  # comparing with corresponding
  # bob entry
  if alice[i] == bob[i]:
   # counting similar entries
   count += 1
 # printing the count  
#main function
def main():
 commontopics("010101", "101101")
 commontopics("111111", "000000")
 commontopics("110000", "110011")
# driver code
if __name__ == "__main__":
# This code is contributed by SrujayReddy



The Time and Space Complexity for all the methods are the same:

Time Complexity: O(n)

Space Complexity: O(n)

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Last Updated : 11 Sep, 2022
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