Simulate the expected number of days to have all devices failed randomly.

main.dart

import 'dart:math';

void main() {
  const int deviceCount = 5;
  const double failRate = 0.5;
  const int sampleCount = 1000;
  
  final random = Random();
  int sum = 0;
  for (int i = 0; i < sampleCount; i += 1) {
    final Set<int> failedDevice = {};
    int t = 0;
    for (; failedDevice.length < deviceCount; t += 1) {
      for (int d = 0; d < deviceCount; d += 1) {
        if (random.nextDouble() <= failRate) {
          failedDevice.add(d);
        }
      }
    }
    sum += t;
  }
  print(sum / sampleCount);
}