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DSA
HardArray

Random Pick with Blacklist

arrayhash tablemath

Problem Statement

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 .

Examples

Example 1
Input:
Output:

Constraints

1 <= n <= 10 ^9
0 <= blacklist.length <= min(10 ^5 , n - 1)
0 <= blacklist[i] < n
All the values of blacklist are unique .
At most 2 * 10 ^4 calls will be made to pick .
😤
Hard
Difficulty
Topic Info
ModuleDSA
CategoryArray
Sub-topicHash Table
Tags
arrayhash tablemathbinary searchsortingrandomized
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