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Felix Pahl joriki

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joriki / Question4611907.java
Created January 16, 2023 23:40
Find binary numbers that generate all n-bit binary numbers using at most one XOR; see https://math.stackexchange.com/questions/4611907.
import java.util.Random;
public class Question4611907 {
final static int k = 52;
final static int n = 10;
final static int m = 1 << n;
final static Random random = new Random();
static int count;
@joriki
joriki / Question4618350a.java
Created January 16, 2023 15:17
Compute the probability that a random permutation of the 54 stickers on a Rubik's cube includes no adjacent squares of the same colour by simulation; see https://math.stackexchange.com/questions/4618350.
public class Question4618350a {
final static int ntrials = 1000000000;
public static void main(String [] args) {
int count = 0;
outer:
for (int n = 0;n < ntrials;n++) {
int [] p = Permutations.getRandomPermutation(54);
for (int square = 0;square < 6;square++) {
@joriki
joriki / Question4618350.java
Last active January 16, 2023 15:15
Compute the probability that a random permutation of the 54 stickers on a Rubik's cube includes no adjacent squares of the same colour; see https://math.stackexchange.com/questions/4618350.
import java.math.BigInteger;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.function.BiConsumer;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
public class Question4618350 {
@joriki
joriki / Question4613898.java
Created January 9, 2023 19:05
count the domino tilings of a rectangle; see https://math.stackexchange.com/questions/4613898
public class Question4613898 {
final static int w = 6;
final static int h = 6;
static int x,y;
static boolean [] [] used = new boolean [w] [h];
static int count;
static int deadEnds;
@joriki
joriki / Question4605602.java
Last active January 9, 2023 19:16
Search the game tree of a repeat-a-number game; see https://math.stackexchange.com/questions/4605602
import java.util.BitSet;
public class Question4605602 {
static BitSet used = new BitSet();
public static void main(String [] args) {
System.out.println(value(1));
}
static boolean value(int move) {
@joriki
joriki / Question4395079.java
Created March 3, 2022 13:06
public class Question4395079 {
public static void main (String [] args) {
int sum = 0;
outer:
for (int i = 1;i <= 99999;i++) {
int bits = 0;
for (char c : String.valueOf(i).toCharArray()) {
int mask = 1 << (c - '0');
if ((bits & mask) != 0)
@joriki
joriki / Question4393372.java
Created March 1, 2022 03:39
import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;
public class Question4393372 {
public static void main(String [] args) {
Set<String> combinations = new HashSet<>();
for (int i = 1000;i < 3000;i++) {
char [] c = String.valueOf(i).toCharArray();
@joriki
joriki / Question4390194b.java
Created February 26, 2022 11:26
import java.util.Random;
public class Question4390194b {
final static Random random = new Random();
final static int ntrials = 100000000;
final static int [] [] families = {
{2,4,6},
{2,3,5},
@joriki
joriki / Question4390194a.java
Last active February 26, 2022 09:42
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
public class Question4390194a {
final static Random random = new Random();
final static int ntrials = 100000000;
final static int [] [] families = {
@joriki
joriki / Question4390194.java
Created February 26, 2022 08:28
import java.util.Random;
public class Question4390194 {
final static Random random = new Random();
final static int ntrials = 100000000;
final static int [] [] families = {
{2,4,6},
{2,3,5},