common_elements.py

'''
Given three arrays sorted in increasing order. Find the elements that are common in all three arrays.

Input:
A = {1, 5, 10, 20, 40, 80}
B = {6, 7, 20, 80, 100}
C = {3, 4, 15, 20, 30, 70, 80, 120}

Output: [20, 80]

Explanation: 20 and 80 are the only
common elements in A, B and C.

'''

def common_elements(arr1,arr2,arr3):
        #Take the lists in set 
        setofarr1 = set(arr1)
        setofarr2 = set(arr2)
        setofarr3 = set(arr3)
        #using the intersection method  we can find out common elements between arr1 and arr2   
        t = setofarr1.intersection(setofarr2)   
        #using the intersection method  we can find out common elements between arr1 and arr2 and arr3  
        Total = list(t.intersection(setofarr3))
        #sort the Total array 
        Total.sort()
        #print out the result 
        return Total

if __name__ == "__main__":
    arr1 = list(map(int,input("Enter the list 1: ").split()))
    arr2 = list(map(int,input("Enter the list 2: ").split()))
    arr3 = list(map(int,input("Enter the list 3: ").split()))
    print("Common elements from all the three lists are ",common_elements(arr1, arr2, arr3))
    
'''
Time Complexity: O(n1 + n2 + n3)
Space Complexity : O(n1 + n2 + n3)

INPUT: 
Enter the list 1: 1 5 10 20 40 80
Enter the list 2: 6 7 20 80 100
Enter the list 3: 3 4 15 20 30 70 80 120 

OUTPUT:
Common elements from all the three lists are  [20, 80]

'''