Random Pick with Blacklist Python Solution

lcpy gen -n 710   # by problem number
lcpy gen -s random_pick_with_blacklist   # by problem name

Input
["Solution", "pick", "pick", "pick", "pick", "pick", "pick", "pick"]
[[7, [2, 3, 5]], [], [], [], [], [], [], []]
Output
[null, 0, 4, 1, 6, 1, 0, 4]

Explanation
Solution solution = new Solution(7, [2, 3, 5]);
solution.pick(); // return 0, any integer from [0,1,4,6] should be ok. Note that for every call of pick,
                 // 0, 1, 4, and 6 must be equally likely to be returned (i.e., with probability 1/4).
solution.pick(); // return 4
solution.pick(); // return 1
solution.pick(); // return 6
solution.pick(); // return 1
solution.pick(); // return 0
solution.pick(); // return 4

import random


class Solution:
    # Time: O(b) init, O(1) pick
    # Space: O(b)
    def __init__(self, n: int, blacklist: list[int]) -> None:
        self.size = n - len(blacklist)
        black = set(blacklist)
        tail = [x for x in range(self.size, n) if x not in black]
        self.remap: dict[int, int] = {}
        for i, b in enumerate(sorted(b for b in black if b < self.size)):
            self.remap[b] = tail[i]

    def pick(self) -> int:
        idx = random.randint(0, self.size - 1)
        return self.remap.get(idx, idx)