HackerRank Python Solution - Sets - No Idea!

There is an array of n integers. There are also 2 disjoint sets, A and B, each containing m integers. You like all the integers in set A and dislike all the integers in set B. Your initial happiness is 0. For each i integer in the array, if i ∊ A, you add 1 to your happiness. If i ∊ B, you add -1 to your happiness. Otherwise, your happiness does not change. Output your final happiness at the end.

Note: Since A and B are set, they have no repeated elements. However, the array might contain duplicate elements.

Constraints:

• 1 <= n <= 10⁵
• 1 <= m <= 10⁵
• 1 <= Any integer in the input <= 10⁹

Input Format:

• The first line contains integers n and m separated by a space.
• The second line contains n integers, the elements of the array.
• The third and fourth lines contain m integers, A and B, respectively.

Output Format:

• Output a single integer, your total happiness.

Sample Input:

3 2
1 5 3
3 1
5 7

Sample Output:

1

Explanation:

• You gain 1 unit of happiness for elements 3 and 1 in set A. You lose 1 unit for 5 in set B. The element 7 in set B does not exist in the array so it is not included in the calculation.
• Hence, the total happiness is 2-1=1.

Solution:

n,m = input().split()

arr = input().split()

A = set(input().split())
B = set(input().split())

print(sum([(i in A) - (i in B) for i in arr]))

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