Skip to content
Related Articles

Related Articles

Improve Article

intersection_update() in Python to find common elements in n arrays

  • Last Updated : 23 Nov, 2020

We are given list of n number of arrays, find all common elements in given arrays ?

Examples:

Input :  arr = [[1,2,3,4],
               [8,7,3,2],
               [9,2,6,3],
               [5,1,2,3]]
Output :  Common Elements = [2,3]

We can solve this problem quickly in python using intersection_update() method of Set() data structure.

How intersection_update() works ?



Suppose we have two sets A and B, then A.intersection_update(B) operation updates set A with common elements in set A and B. For example, A=set([1,2,3]) and B=set([4,2,3]) now after taking A.intersection_update(B), value of set A will be [2,3]. Syntax is anySet.intersection_update(iterable).




# Function to find common elements in n arrays 
def commonElements(arr): 
      
    # initialize result with first array as a set 
    result = set(arr[0]) 
  
    # now iterate through list of arrays starting from 
    # second array and take intersection_update() of 
    # each array with result. Every operation will 
    # update value of result with common values in 
    # result set and intersected set 
    for currSet in arr[1:]: 
        result.intersection_update(currSet) 
  
    return list(result) 
  
# Driver code 
if __name__ == "__main__"
    arr = [[1,2,3,4], [8,7,3,2], [9,2,6,3], [5,1,2,3]] 
    output = commonElements(arr) 
    if len(output) > 0
        print ("Common Element = ",output) 
    else
        print ('No Common Elements Found')

Output:

Common Elements = [2,3]

This article is contributed by Shashank Mishra (Gullu). If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.

Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.  To complete your preparation from learning a language to DS Algo and many more,  please refer Complete Interview Preparation Course.

In case you wish to attend live classes with experts, please refer DSA Live Classes for Working Professionals and Competitive Programming Live for Students.




My Personal Notes arrow_drop_up
Recommended Articles
Page :