Submission #189401

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Source Code Expand

import java.util.Scanner;

public class Main {

    public static double[][] ptriangle(int n) {
        if (n == 0)
            return new double[0][0];
        double[][] field = new double[n + 2][n + 1];
        int l = n + 1;
        field[0][0] = 1.0;
        for (int i = 1; i <= l; i++) {
            field[i][0] = field[i - 1][0] / 2;
            for (int j = 1; j < l; j++) {
                field[i][j] = (field[i - 1][j - 1] + field[i - 1][j]) / 2;
            }
        }
        return field;
    }

    static double[][] pt = null;

    static double solve() throws Exception {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int d = sc.nextInt();
        int x = Math.abs(sc.nextInt());
        int y = Math.abs(sc.nextInt());
        int px = x / d, py = y / d;
        if (x % d > 0 || y % d > 0 || px+py > n) return 0.0;
        double ans = 0.0;
        pt = ptriangle(n);
        for (int xx = 0; xx <= n; xx++) {
            int yy = n - xx;
            if ((xx - px) % 2 > 0 || (yy - py) % 2 > 0) continue;
            ans += pt[n][xx] * pt[xx][ px + (xx - px) / 2] * pt[yy][ py + (yy - py) / 2];
        }
        return ans;
    }

    public static void main(String... args) throws Exception {
        System.out.println(solve());
    }
}

Submission Info

Judge Result