398. 随机数索引

import random
from collections import defaultdict
from functools import reduce
from typing import Dict, Tuple, List


class Solution:

    def __init__(self, nums: List[int]):
        def func(val, ele):
            i, v = ele
            val[v].append(i)
            return val

        self.data = reduce(func, enumerate(nums), defaultdict(list))

    def pick(self, target: int) -> int:
        return random.choice(self.data[target])