Submission #187984

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Source Code Expand

import java.math.BigDecimal;
import java.util.Scanner;

/**
 * Created by hama_du on 2014/06/21.
 */
public class Main {
    public static void main(String[] args) {
        BigDecimal[][] C = new BigDecimal[1001][1001];
        for (int i = 0 ; i <= 1000 ; i++) {
            C[i][0] = BigDecimal.ONE;
            C[i][i] = BigDecimal.ONE;
            for (int j = 1 ; j < i ; j++) {
                C[i][j] = BigDecimal.ZERO.add(C[i-1][j-1]).add(C[i-1][j]);
            }
        }

        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int d = in.nextInt();
        int x = in.nextInt();
        int y = in.nextInt();
        if (Math.abs(x) % d != 0 || Math.abs(y) % d != 0) {
            System.out.println(0.0d);
            return;
        }
        int xneed = Math.abs(x) / d;
        int yneed = Math.abs(y) / d;
        int need = xneed + yneed;
        if (need > n || need % 2 != n % 2) {
            System.out.println(0.0d);
            return;
        }

        BigDecimal p = BigDecimal.valueOf(0.0d);
        for (int xn = 0 ; xn <= n ; xn++) {
            int yn = n - xn;
            if (xn < xneed || xn % 2 != xneed % 2) {
                continue;
            }
            if (yn < yneed || yn % 2 != yneed % 2) {
                continue;
            }
            int left = (xn - xneed) / 2;
            int right = (xn + xneed) / 2;
            int down = (yn - yneed) / 2;
            int up = (yn + yneed) / 2;
            BigDecimal add = BigDecimal.ONE
                    .multiply(C[n][left])
                    .multiply(C[n - left][right])
                    .multiply(C[n - left - right][down]);
            p = p.add(add);
        }

        BigDecimal p4 = BigDecimal.valueOf(1L);
        for (int i = 0 ; i < n ; i++) {
            p4 = p4.multiply(BigDecimal.valueOf(4L));
        }
        BigDecimal answer = p.divide(p4, 12, BigDecimal.ROUND_HALF_UP);
        System.out.println(answer.toString());
    }

}

Submission Info

Judge Result