joriki’s gists

joriki / Question4390837.java

Created February 26, 2022 07:42

	import java.io.FileOutputStream;
	import java.io.IOException;
	import java.io.PrintStream;
	import java.util.Random;

	public class Question4390837 {
	final static int a = 2;
	final static int b = 2;

	final static int ntrials = 100000000;

joriki / WorldRankingExtracter.java

Created July 30, 2021 18:09

	package games.chess.fide;

	import java.io.IOException;

	import org.jsoup.Jsoup;
	import org.jsoup.nodes.Element;

	public class WorldRankingExtracter {
	public static void main(String [] args) throws IOException {
	int rank = 0;

joriki / Question3706460.java

Last active June 5, 2020 05:44

Count the binary strings that can be generated by alternatingly adding zeros and ones to either end; see https://math.stackexchange.com/questions/3706460.

	import java.util.HashSet;
	import java.util.Set;

	public class Question3706460 {
	public static void main(String [] args) {
	Set<Long> strings = new HashSet<>();
	strings.add(1L);
	long bit = 2;
	boolean one = false;
	for (int n = 1;;n++,bit <<= 1,one = !one) {

joriki / Question3674864.java

Created May 14, 2020 19:17

Simulate how long it takes until six dice that retain a 1 for 4 turns all show a 1; see https://math.stackexchange.com/questions/3674864.

	import java.util.Random;

	public class Question3674864 {
	final static long ntrials = 10000000;
	final static Random random = new Random();

	public static void main (String [] args) {
	long count = 0;
	for (long trial = 0;trial < ntrials;trial++) {
	int [] state = new int [6];

joriki / Question3674784.java

Created May 14, 2020 16:55

Find perfect squares whose difference is a repunit; see https://math.stackexchange.com/questions/3674784.

	import java.math.BigInteger;

	public class Question3674784 {
	public static void main(String [] args) {
	for (int n = 1;;n++) {
	System.out.println(n);
	BigInteger diff = BigInteger.TEN.pow(n).subtract(BigInteger.ONE).divide(BigInteger.TEN.subtract(BigInteger.ONE));
	BigInteger x = BigInteger.TWO;
	BigInteger x2 = x.multiply(x);
	BigInteger y = BigInteger.ONE;

joriki / Question3667404.java

Created May 11, 2020 03:59

Simulate the number of uniformly distributed quarter circle sectors required to cover a circle; see https://math.stackexchange.com/questions/3667404.

	import java.util.ArrayList;
	import java.util.Iterator;
	import java.util.List;
	import java.util.Random;

	public class Question3667404 {
	final static long ntrials = 10000000;
	final static Random random = new Random();

	static class Range {

joriki / Question3664030.java

Created May 8, 2020 06:55

Count intervals of size 1/n hit by the numbers 1/k; see https://math.stackexchange.com/questions/3664030.

	public class Question3664030 {
	public static void main(String [] args) {
	for (int n = 1;n < 2000;n++) {
	int count = 0;
	boolean [] hit = new boolean [n];
	for (int k = 1;k <= n + 1;k++) {
	double x = 1. / k;
	// to count values on boundaries only towards the lower interval, subtract 1e-12 here ...
	int index = (int) (n * x);
	if (index < n && !hit [index]) {

joriki / Question3629762.java

Created April 17, 2020 19:23

Find all magic 4x4 squares in which the sum in each 2x2 subsquare is the magic sum; see https://math.stackexchange.com/questions/3629762.

	import java.util.ArrayList;
	import java.util.Arrays;
	import java.util.List;

	public class Question3629762 {
	static class Constraint {
	int [] cells;
	int sum;

	public Constraint(int [] cells) {

joriki / Question3629474.java

Created April 17, 2020 05:38

Simulate the angle between two vectors uniformly randomly picked in the unit square; see https://math.stackexchange.com/questions/3629474.

	import java.util.Random;

	public class Question3629474 {
	final static long ntrials = 100000000;
	final static Random random = new Random();

	public static void main(String [] args) {
	double sum = 0;
	for (long n = 0;n < ntrials;n++)
	sum += Math.abs(angle() - angle());

joriki / Question3620483.java

Created April 13, 2020 15:35

Calculate a term in the expansion of the fraction of configurations that don't cause a black hole to form; see https://math.stackexchange.com/questions/3620483.

	import java.util.ArrayList;
	import java.util.Arrays;
	import java.util.List;
	import java.util.function.Consumer;
	import java.util.stream.Collectors;

	import BallsInBins; // https://gist.github.com/joriki/d324726fbc3fe4ccdf33628aa02b790c
	import BigRational; // https://gist.github.com/joriki/3097452fbb9e1983daf1035f57e72722
	import Binomials; // https://gist.github.com/joriki/5a5c03d2c286effa69584e77a064a6e3

Felix Pahl joriki