/* vim: set expandtab tabstop=4 shiftwidth=4 : */

public class PercolationStats
{
    private double[] results;
    private double mean;
    private double stddev;
    private int N;

    // perform T independent computational experiments on an N-by-N grid
    public PercolationStats(int N, int T)
    {
        if (N < 1 || T < 1)
            throw new java.lang.IllegalArgumentException("received value < 1");
        this.N = N;
        results = new double[T];
        int n = N*N;
        for (int t = 0; t < T; t++)
        {
            double c = 0;
            Percolation p = new Percolation(N);
            do
            {
                int i = StdRandom.uniform(1, N+1);
                int j = StdRandom.uniform(1, N+1);
                if (!p.isOpen(i, j)) {
                    p.open(i, j);
                    c += 1;
                }
            }
            while(!p.percolates());
            results[t] = c / n;
        }
        mean = StdStats.mean(results);
        stddev = StdStats.stddev(results);
    }

    // sample mean of percolation threshold
    public double mean()
    {
        return mean;
    }

    // sample standard deviation of percolation threshold
    public double stddev()
    {
        return stddev;
    }

    // returns lower bound of the 95% confidence interval
    public double confidenceLo()
    {
        return mean - 1.96*stddev/Math.sqrt(N);
    }

    // returns upper bound of the 95% confidence interval
    public double confidenceHi()
    {
        return mean + 1.96*stddev/Math.sqrt(N);
    }

    // test client
    public static void main(String[] args) {
        int N = Integer.parseInt(args[0]);
        int T = Integer.parseInt(args[1]);
        PercolationStats stats = new PercolationStats(N, T);
        System.out.printf("mean                    = %.16f\n", stats.mean());
        System.out.printf("stddev                  = %.16f\n", stats.stddev());
        System.out.printf("95%% confidence interval = %.16f, %.16f\n\n",
                stats.confidenceLo(), stats.confidenceHi());
    }
}