toxophily_lzx.java

第四届百度杯编程大赛final解题报告+标程

import java.io.*;
import java.math.*;
import java.util.Scanner;
import java.text.DecimalFormat;

public class Toxophily_lzx {
    public static void main(String[] args) throws IOException {
        final double epsilon = 1e-8;
        final double g = 9.8;
        Scanner in = new Scanner(System.in);
        DecimalFormat ctrl = new DecimalFormat("0.000000");
        int T = in.nextInt();
        while (T-- > 0) {
            double x = in.nextDouble(), y = in.nextDouble(), v = in.nextDouble();
            if (v < epsilon) {
            	System.out.println(-1);
                continue;
            }
            if (Math.abs(x) < epsilon) {
                if (2 * g * y > v * v) {
                	System.out.println(-1);
                }
                else {
                	System.out.println(ctrl.format(Math.PI / 2));
                }
                continue;
            }
            double t = (g * x * x) / (v * v);
            double delta = x * x - (2 * y + t) * t;
            if (Math.abs(delta) < epsilon) {
            	System.out.println(ctrl.format(Math.atan(x / t)));
            }
            else if (delta < 0) {
                System.out.println("-1");
            }
            else {
                double res = Math.min(Math.atan((x - Math.sqrt(delta)) / t), Math.atan((x + Math.sqrt(delta)) / t));
                System.out.println(ctrl.format(res));
            }
        }
    }
}