SickSimulation

Simulation.java

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import org.apache.commons.lang.math.RandomUtils;

public class Simulation {

  static int N = 8000000;
  static int ROUNDS = 24;
  static int INITIAL_SICKS = 5000;
  static int INITIAL_TESTS = 100;

  static boolean pop[] = new boolean[N];

  private static void infect(int number) {
    for (int i = 0; i < number; i++) {
      int idx = RandomUtils.nextInt(N);
      int j = 0;
      while (j < N) {
        if (!pop[(idx + j) % N]) {
          pop[(idx + j) % N] = true;
          break;
        }
        j++;
      }
    }

  }

  private static int getNewCheck(Set<Integer> checked) {
    while (true) {
      int idx = RandomUtils.nextInt(N);
      if (!checked.contains(idx)) {
        checked.add(idx);
        return idx;
      }
    }
  }

  private static int sample(int number) {
    int sick = 0;
    number = Math.min(number, N);
    Set<Integer> checked = new HashSet<>();
    for (int i = 0; i < number; i++) {
      if (pop[getNewCheck(checked)]) {
        sick++;
      }
    }
    return sick;
  }

  public static void main(String[] args) {
    int sicksToday = INITIAL_SICKS;
    int testsToday = INITIAL_TESTS;
    int idx = RandomUtils.nextInt(N);
    pop[idx] = true;
    List<Integer> results = new ArrayList<>();
    for (int i = 0; i < ROUNDS; i++) {
      sicksToday *= 1.2;
      testsToday *= 1.1;
//      testsToday = sicksToday/2;
      infect(sicksToday);
      int numToCheck = Math.min(testsToday, N);
      int foundToday = sample(numToCheck);
      int percents = (int) (((double) foundToday / (double) numToCheck) * 100.0);
      results.add(percents);
      System.out.println("Number of tests: " + numToCheck + ", number of actual sick: " + sicksToday
          + ", found today: " + foundToday + ", %"
          + percents);
    }

    System.out.println();
    System.out.println("Percents:");
    for (Integer result : results) {
      System.out.println(result);
    }
  }
}