因为字典是无序的，用列表去保存set、get操作的顺序

class Solution:
    def LRU(self , operators: List[List[int]], k: int) -> List[int]:
        # write code here
        opt_dict, opt_list = {}, []

        def set(key, val):
            if len(opt_list) < k:
                opt_dict[key] = val
                opt_list.append(key)
            else:
                del opt_dict[opt_list.pop(0)]
                opt_dict[key] = val
                opt_list.append(key)

        def get(key):
            if key in opt_dict.keys():
                opt_list.remove(key)
                opt_list.append(key)
                return opt_dict[key]
            else:
                return -1

        sol = []
        for l in operators:
            if l[0] == 1: set(l[1], l[2])
            else:
                sol.append(get(l[1]))
        return sol