Package g0701_0800.s0710_random_pick_with_blacklist

Class Solution

java.lang.Object
g0701_0800.s0710_random_pick_with_blacklist.Solution
public class Solution extends Object
710 - Random Pick with Blacklist\. Hard You are given an integer `n` and an array of **unique** integers `blacklist`. Design an algorithm to pick a random integer in the range `[0, n - 1]` that is **not** in `blacklist`. Any integer that is in the mentioned range and not in `blacklist` should be **equally likely** to be returned. Optimize your algorithm such that it minimizes the number of calls to the **built-in** random function of your language. Implement the `Solution` class: * `Solution(int n, int[] blacklist)` Initializes the object with the integer `n` and the blacklisted integers `blacklist`. * `int pick()` Returns a random integer in the range `[0, n - 1]` and not in `blacklist`. **Example 1:** **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 **Constraints:** * 1 <= n <= 109 * 0 <= blacklist.length <- min(105, n - 1) * `0 <= blacklist[i] < n` * All the values of `blacklist` are **unique**. * At most 2 * 104 calls will be made to `pick`.

  • Constructor Details

    • Solution

      public Solution(int n, int[] blacklist)

  • Method Details

    • pick

      public int pick()