Fruit into Baskets

class Solution:
    def totalFruit(self, fruits):
        types = {}
        back = 0
        res = 0

        for front in range(len(fruits)):
            types[fruits[front]] = 1 + types.get(fruits[front], 0)

            # release
            while len(types) >=3:
                types[fruits[back]] = types.get(fruits[back]) - 1
                if types[fruits[back]] == 0:
                    del types[fruits[back]]
                back += 1

            res = max(res, front - back + 1)
        return (res)

# find the longest subarray that has at most 2 different numbers