公平的交换糖果

#公平的糖果交换

def func(A,B):
    sum_a = sum(A)
    sum_b = sum(B)
    setB = set(B)
    for x in A:
        if x+(sum_b-sum_a)//2 in setB:
            return [x,int(x+(sum_b-sum_a)//2)]
        else:
            return []


B=[2]
A=[1,3]
print(func(A,B))