# Python program to find common elements in three lists using sets

PythonProgrammingServer Side Programming

Given three user input lists, our task is to find out common elements from these three lists. Here we are applying intersection method.

## Example

Input
A=[2, 3, 4, 5, 6]
B=[2, 3, 7, 6, 90]
C=[2, 3, 45, 34]
Common elements=[2, 3]


## Algorithm

Step1: input the elements of three lists.
Step2: Use intersection method, first convert lists to sets then apply intersection method of two sets and find out common elements then this set intersect with the third set.


## Example code

def common_ele(my_A, my_B, my_C):
my_s1 = set(my_A)
my_s2 = set(my_B)
my_s3 = set(my_C)
my_set1 = my_s1.intersection(my_s2)
output_set = my_set1.intersection(my_s3)
output_list = list(output_set)
print(output_list)
if __name__ == '__main__' :
# First List
A=list()
n=int(input("Enter the size of the List"))
print("Enter the number")
for i in range(int(n)):
p=int(input("Size="))
A.append(int(p))
print (A)
# Second List
B=list()
n1=int(input("Enter the size of the List"))
print("Enter the number")
for i in range(int(n1)):
p=int(input("Size="))
B.append(int(p))
print (B)
# Third Array
C=list()
n2=int(input("Enter the size of the List"))
print("Enter the number")
for i in range(int(n2)):
p=int(input("Size="))
C.append(int(p))
print (C)
# Calling Function
common_ele(A, B, C)


## Output

Enter the size of the List 3
Enter the number
Size= 2

Size= 1
[2, 1]
Size= 2
[2, 1, 2]
Enter the size of the List 3
Enter the number
Size= 2

Size= 1
[2, 1]
Size= 4
[2, 1, 4]
Enter the size of the List 4
Enter the number
Size= 3

[]
Size= 2
[3, 2]

Size= 1
[3, 2, 1]
[1, 2]
Size= 3
[3, 2, 1, 3]
[1, 2]