User:Margusmartsepp/Contributions/Java/Utils.java

<lang java> import java.util.ArrayList; import java.util.Collections;

public class Utils<T extends Comparable<T>> { private void swap(ArrayList<T> data, int i, int j) { T t = data.get(i); data.set(i, data.get(j)); data.set(j, t); }

public ArrayList<Integer> mRange(int from, int to) { ArrayList<Integer> result = new ArrayList<Integer>(); for (int i = from; i <= to; i++) result.add(i); return result; }

public boolean nextPerm(ArrayList<T> data) { // find the swaps int c = -1, d = data.size(); for (int i = d - 2; i >= 0; i--) if (data.get(i).compareTo(data.get(i + 1)) < 0) { c = i; break; }

if (c < 0) return false;

int s = c + 1; for (int j = c + 2; j < d; j++) if (data.get(j).compareTo(data.get(s)) < 0 && // data.get(j).compareTo(data.get(c)) > 0) s = j;

// do the swaps swap(data, c, s); while (--d > ++c) swap(data, c, d);

return true; }

@SuppressWarnings("unchecked") public ArrayList<ArrayList<T>> Permutations(ArrayList<T> d) { ArrayList<ArrayList<T>> result = new ArrayList<ArrayList<T>>(); Collections.sort(d); do { result.add((ArrayList<T>) d.clone()); } while (this.nextPerm(d)); return result; } } </lang>