airplane-boarding-problem.rs

use rand::prelude::*;
use std::collections::HashSet;

fn main() {
    let num_iterations = 1_000_000;
    let mut rng = thread_rng();
    let mut successful_run_count = 0;
    
    for _ in 0..num_iterations {  // Fixed syntax here
        if single_trial(100, &mut rng) {
            successful_run_count += 1;
        }
    }
    
    let result_probability = successful_run_count as f64 / num_iterations as f64;
    println!(
        "After {} trials, the estimated probability that the last passenger sits in their own seat is {:.6}",
        num_iterations,
        result_probability
    );
}

fn single_trial(total_passengers: usize, rng: &mut impl Rng) -> bool {
    let mut available_seats: HashSet<usize> = (0..total_passengers).collect();
    
    // First passenger chooses randomly
    let initial_seat = *available_seats.iter().choose(rng).unwrap();
    available_seats.remove(&initial_seat);
    
    // Process all passengers except the last one
    for passenger in 1..(total_passengers - 1) {
        if !available_seats.remove(&passenger) {
            // If assigned seat is taken, choose randomly from remaining seats
            let random_seat = *available_seats.iter().choose(rng).unwrap();
            available_seats.remove(&random_seat);
        }
    }
    
    // Check if last passenger gets their assigned seat
    *available_seats.iter().next().unwrap() == total_passengers - 1
}