4129433_ac_516ms_4936k.java

北大大牛代码 1240道题的原代码 超级权威

import java.util.*;

public class Main {
	private Scanner in;

	public static void main(String[] args) {
		new Main().run();
	}

	private void run() {
		int n;
		double xa, ya, xb, yb;

		in = new Scanner(System.in);
		while (true) {
			n = in.nextInt();
			if (n == 0) {
				break;
			}
			xa = in.nextDouble();
			ya = in.nextDouble();
			xb = in.nextDouble();
			yb = in.nextDouble();
			double ans = 0.00;
			double size = 0.0;
			for (int i = 0; i < n; i++) {
				double len = in.nextDouble();
				ans -= len * len / 2.0;
				size += Math.sqrt(len * len * 2);
			}
			double min = 0, mid;
			double max = 100000;
			while (min + 1e-10 < max) {
				mid = (min + max) / 2.0;
				double x, y;
				if (xa == 0) {
					x = 0;y = mid;
				} else {
					if (ya == 0) {
						x = mid;y = 0;
					}
					else {
						x = mid * xa / (xa + ya);
						y = mid * ya / (xa + ya);
					}
				}
				double X, Y;
				if (xb == 0) {
					X = 0;Y = mid;
				} else {
					if (yb == 0) {
						X = mid;Y = 0;
					}
					else {
						X = mid * xb / (xb + yb);
						Y = mid * yb / (xb + yb);
					}
				}
				double dis = Math.hypot(x - X, y - Y);
				if (Math.abs(dis - size) < 1e-10) {
					double a = Math.hypot(X, Y);
					double b = Math.hypot(x, y);
					double p = (a + b + size) / 2.0;
					ans += Math.sqrt(p * (p - a) * (p - b) * (p - size));
					break;
				}
				if (dis < size) {
					min = mid;
				} else {
					max = mid;
				}
			}
			System.out.printf("%.3f\n", ans);
		}
	}
}