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

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Given three arrays, we have to find common elements in three sorted lists using sets.

Examples:

` Input: ar1 = [1, 5, 10, 20, 40 , 80] ar2 = [6, 7, 20, 80, 100] ar3 = [3, 4, 15, 20, 30, 70, 80, 120] Output: [80, 20] Input: ar1 = [1, 5 , 5] ar2 = [3, 4, 5, 5, 10] ar3 = [5, 5, 10, 20] Output:  `

Fit:
We have given three arrays, with the help of sets you can easily find the intersection of these arrays.

The intersection method simply ensures the intersection of both arrays on which you want to perform the intersection operation (or simply gives the common elements in both arrays). We will take three arrays and then select an intersection.

Below is the implementation of the above approach:

 ` # Python3 program for finding common elements ` ` # in three lists using sets `   ` def ` ` IntersecOfSets (arr1, arr2, arr3): ` ` # Convert arrays to sets ` ` ` ` s1 ` ` = ` ` set ` ` (arr1) ` ` s2 ` ` = ` ` set ` ` (arr2) ` ` ` ` s3 ` ` = ` ` set ` ` (arr3) `   ` # Calculates intersection ` ` # sets to s1 and s2 ` ` set1 ` ` = ` ` s1.intersection (s2) ` ` # [80, 20, 100] `   ` # Calculates set intersection ` ` # on set1 and s3 ` ` result_set ` ` = ` ` set1.inter section (s3) `   ` # Converts the result set to a list ` ` final_list ` ` = ` ` list ` ` (result_set) ` ` print ` ` (final_list) ` ` `  ` Driver code ` ` if ` ` __ name__ ` ` = ` ` = ` ` ’__main__’ ` `: `   ` # Array items ` ` arr1 ` ` = ` ` [` ` 1 ` `, ` ` 5 ` `, ` ` 10 ` `, ` ` 20 ` `, ` ` 40 ` `, ` ` 80 ` `, ` ` 100 ` `] `   ` # Elements in Array2 ` ` ` ` arr2 ` ` = ` ` [` ` 6 ` `, ` ` 7 ` `, ` ` 20 ` `, ` ` 80 ` `, ` ` 100 ` `] `   ` # Elements in Array3 ` ` arr3 ` ` = ` ` [` ` 3 ` `, ` ` 4 ` `, ` ` 15 ` `, ` ` 20 ` `, ` ` 30 ` `, ` ` 70 ` `, ` ` 80 ` `, ` ` 120 ` `] `   ` # Function call ` ` Inters ecOfSets (arr1, arr2, arr3) `

Output:

` [80, 20] `

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