Question

How to generate a random integer from a range [0, N] that is not in a unique integer list with Java

Answer 1

import java.util.Arrays;
import java.util.Random;
import java.util.List;

public class RandomExcluding {

    public static int randomExcluding(int N, List<Integer> excluded) {
        if (excluded.size() > N + 1) {
            return -1; // All numbers are excluded
        }

        Random rand = new Random();
        int num;
        do {
            num = rand.nextInt(N + 1);
        } while (excluded.contains(num));

        return num;
    }

    public static void main(String[] args) {
        List<Integer> excluded = Arrays.asList(2, 5, 7);
        int N = 14;

        int result = randomExcluding(N, excluded);
        System.out.println(result);
    }
}


/*
run:

6

*/

 

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