joriki’s gists

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

joriki / BigRational.java

Created April 13, 2020 15:28

Big rationals, much like big integers.

	import java.math.BigInteger;

	public class BigRational implements Comparable<BigRational> {
	public static BigRational ZERO = new BigRational (0);
	public static BigRational ONE = new BigRational (1);

	BigInteger num;
	BigInteger den;

	public BigRational(long n) {

joriki / Question3620950.java

Created April 12, 2020 01:13

Calculate abc-conjecture qualities for c,a power of three and two, respectively; see https://math.stackexchange.com/questions/3620950.

	import java.io.IOException;
	import java.math.BigInteger;
	import java.util.Arrays;
	import java.util.Locale;

	public class Question3620950 {
	final static long n = 0x80000000L;

	public static void main (String [] args) {
	boolean [] prime = new boolean [(int) (n >> 1)]; // prime [i] : is 2i + 1 prime?

joriki / Question3617128.java

Created April 9, 2020 12:10

Find poetic derangements; see https://math.stackexchange.com/questions/3617128.

	public class Question3617128 {
	static long count;

	public static void main(String [] args) {
	for (int i = 1,n = 1;;i++,n += i) {
	count = 0;
	recurse (new boolean [n],new int [n],new int [i + 1],0);
	System.out.println(n + " : " + count);
	}
	}

joriki / Question3609799.java

Created April 5, 2020 07:50

Find possible factors from two elements of a shuffle product; see https://math.stackexchange.com/questions/3609799.

	import java.util.Arrays;
	import java.util.HashSet;
	import java.util.Random;
	import java.util.Set;

	public class Question3609799 {
	final static int k = 20;
	final static int l = 30;
	final static int n = k + l;

joriki / Question2257188.java

Created April 2, 2020 15:46

Compute the variance of a random variable in a coin experiment; see https://math.stackexchange.com/questions/2257188.

	public class Question2257188 {
	final static int n = 4;

	public static void main(String [] args) {
	double s = 0;
	double s2 = 0;
	int [] [] permutations = Permutations.getPermutations(n);
	for (int [] p : permutations) {
	int sum = p [0] + 1;
	for (int i = 1;i < p.length;i++)

joriki / Question3606037.java

Created April 2, 2020 10:50

Simulate the expected average of dice rolls if the first roll is 1 and the trial ends when a roll repeats; see https://math.stackexchange.com/questions/3606037.

	import java.util.Random;

	public class Question3606037 {
	final static long ntrials = 100000000;
	final static Random random = new Random();

	public static void main(String [] args) {
	double total = 0;
	for (long n = 0;n < ntrials;n++) {
	double sum = 1;

joriki / Question3605591.java

Created April 2, 2020 05:36

Apply various methods of apportioning seats in a parliament; see https://math.stackexchange.com/questions/3605591.

	import java.io.IOException;
	import java.util.Arrays;
	import java.util.Comparator;
	import java.util.HashMap;
	import java.util.HashSet;
	import java.util.Map;
	import java.util.PriorityQueue;
	import java.util.Queue;
	import java.util.Set;

joriki / Question3602087a.java

Created March 31, 2020 12:02

Calculate the exaxt probability distribution for the number of pairs of consecutive cards with matching suits; see https://math.stackexchange.com/questions/3602087.

	package temp;

	import java.math.BigInteger;
	import java.util.Arrays;
	import java.util.HashMap;
	import java.util.Map;

	public class Question3602087a {
	final static int NSUITS = 4;
	final static int NRANKS = 13;

joriki / Question3602087

Created March 31, 2020 06:39

Simulate the expected number of suit matches in pairs of consecutive cards in a standard 52-card deck; see https://math.stackexchange.com/questions/3602087.

	import java.util.Random;

	public class Question3602087 {
	final static long ntrials = 10000000;

	final static Random random = new Random();

	final static int NSUITS = 4;
	final static int NRANKS = 13;
	final static int NCARDS = NRANKS * NSUITS;

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