87 lines
2.4 KiB
Java
87 lines
2.4 KiB
Java
import java.util.ArrayList;
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import java.util.Collections;
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import java.util.Iterator;
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import java.util.List;
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import java.util.Objects;
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public class RandomLatinSquares {
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private static void printSquare(List<List<Integer>> latin) {
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for (List<Integer> row : latin) {
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Iterator<Integer> it = row.iterator();
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System.out.print("[");
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if (it.hasNext()) {
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Integer col = it.next();
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System.out.print(col);
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}
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while (it.hasNext()) {
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Integer col = it.next();
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System.out.print(", ");
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System.out.print(col);
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}
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System.out.println("]");
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}
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System.out.println();
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}
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private static void latinSquare(int n) {
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if (n <= 0) {
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System.out.println("[]");
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return;
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}
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List<List<Integer>> latin = new ArrayList<>(n);
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for (int i = 0; i < n; ++i) {
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List<Integer> inner = new ArrayList<>(n);
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for (int j = 0; j < n; ++j) {
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inner.add(j);
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}
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latin.add(inner);
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}
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// first row
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Collections.shuffle(latin.get(0));
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// middle row(s)
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for (int i = 1; i < n - 1; ++i) {
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boolean shuffled = false;
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shuffling:
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while (!shuffled) {
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Collections.shuffle(latin.get(i));
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for (int k = 0; k < i; ++k) {
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for (int j = 0; j < n; ++j) {
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if (Objects.equals(latin.get(k).get(j), latin.get(i).get(j))) {
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continue shuffling;
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}
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}
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}
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shuffled = true;
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}
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}
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// last row
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for (int j = 0; j < n; ++j) {
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List<Boolean> used = new ArrayList<>(n);
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for (int i = 0; i < n; ++i) {
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used.add(false);
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}
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for (int i = 0; i < n - 1; ++i) {
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used.set(latin.get(i).get(j), true);
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}
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for (int k = 0; k < n; ++k) {
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if (!used.get(k)) {
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latin.get(n - 1).set(j, k);
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break;
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}
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}
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}
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printSquare(latin);
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}
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public static void main(String[] args) {
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latinSquare(5);
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latinSquare(5);
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latinSquare(10);
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}
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}
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