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export default class Solution {    #array: Array<number>;    #black: Set<number>;    #n: number;    constructor(n: number, blacklist: number[]) {        this.#n = n;        const black = new Set(blacklist);        this.#black = black;        this.#array = new Array<number>();        if (            n - blacklist.length <= 50000 &&            (n - blacklist.length) / n <= 0.5        ) {            for (let i = 0; i < n; i++) {                if (!black.has(i)) {                    this.#array.push(i);                }            }        }    }
    pick(): number {        if (this.#array.length) {            const index = Math.floor(Math.random() * this.#array.length);            return this.#array[index];        } else {            while (true) {                const index = Math.floor(Math.random() * this.#n);
                if (!this.#black.has(index)) {                    return index;                }            }        }    }}