Lottery: test de programación by Spotify

Solución en Java para el problema de la lotería expuesto por Spotify. Para resolverlo hay que tener claro el concepto de probabilidad en conjuntos. Para ver en detalle el código acceder al siguiente enlace.

	import java.util.Scanner;
	import java.io.BufferedInputStream;
	public class Lottery {
	public static double LotteryProbability (String lottery) {
	int m=0,n=0,t=0,p=0,requiredForWin=0;
	double result=0.0;
	String[] number = lottery.split(" ");
	m=Integer.parseInt(number[0]);
	n=Integer.parseInt(number[1]);
	t=Integer.parseInt(number[2]);
	p=Integer.parseInt(number[3]);
	requiredForWin=(int)Math.ceil((double)p/t);
	if (requiredForWin>n) { return result; }
	for (int i=requiredForWin;i<(Math.min(n,p)+1);i++) {
	result+=probability(i,p,n,m);
	}
	return result;
	}
	private static double probability (int x, int p, int n, int m) {
	double result=0.0,y=0.0;
	y=combination(m,n);
	if (y==0.0) { return result; } else {
	result=combination(p, x)*combination(m-p, n-x)/y;
	}
	return result;
	}
	private static double combination(int n, int m) {
	double result=1.0;
	if ((m<0)||(m>n)) { return 0.0; }
	if (m>(n-m)) { m=(n-m); }
	for (int i=0;i<m;i++) {
	result=result*(n-(m-(i+1)));
	result=result/(i+1);
	}
	return result;
	}
	public static boolean validEntry (String line) {
	int val1=0,val2=0,val3=0,val4=0;
	boolean result=true;
	String[] number = line.split(" ");
	if (number.length==4) {
	String n_line= new String (line.replaceAll("[0-9]+", ""));
	if (n_line.length()!=3) { result=false; } else {
	val1=Integer.parseInt(number[0]);
	val2=Integer.parseInt(number[1]);
	val3=Integer.parseInt(number[2]);
	val4=Integer.parseInt(number[3]);
	if ((val1<1)||(val2<1)||(val3<1)||(val4<1)) { result=false; }
	if ((val1>1000)||(val2>val1)||(val3>100)||(val4>val1)) { result=false; }
	}
	} else {
	result=false;
	}
	return result;
	}
	public static void main(String[] args) {
	try {
	double result=0.0;
	Scanner sca = new Scanner(new BufferedInputStream(System.in));
	String line = sca.nextLine();
	if (validEntry(line)) { result=LotteryProbability(line); }
	System.out.printf("%.10f\n", result);
	} catch (Exception e) {
	System.err.println("Error: " + e.getMessage());
	}
	}
	}

view raw Lottery.java hosted with ❤ by GitHub