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/* ==========================================
* JGraphT : a free Java graph-theory library
* ==========================================
*
* Project Info: http://jgrapht.sourceforge.net/
* Project Creator: Barak Naveh (http://sourceforge.net/users/barak_naveh)
*
* (C) Copyright 2003-2008, by Barak Naveh and Contributors.
*
* This program and the accompanying materials are dual-licensed under
* either
*
* (a) the terms of the GNU Lesser General Public License version 2.1
* as published by the Free Software Foundation, or (at your option) any
* later version.
*
* or (per the licensee's choosing)
*
* (b) the terms of the Eclipse Public License v1.0 as published by
* the Eclipse Foundation.
*/
/* -----------------
* IntegerPermutationIter.java
* -----------------
* (C) Copyright 2005-2008, by Assaf Lehr and Contributors.
*
* Original Author: Assaf Lehr
* Contributor(s): -
*
* $Id$
*
* Changes
* -------
*/
package org.jgrapht.experimental.permutation;
import java.util.*;
/**
* Iterates through permutations of N elements.
*
*
*
use getNext() to get the next permutation order, for example(N=4):
* perm0=[1,2,3,4] perm1=[1,2,4,3] perm2=[1,3,2,4] .
*
use hasNext() or verify by counter<getTotalNumberOfPermutations ()
* that you do not overflow the max number. RunTimeException will be thrown if
* you do. Getting the next permutation is done in O(N) Note: This class is not
* thread safe.
*
*
* @author Assaf
* @since May 20, 2005
*/
public class IntegerPermutationIter
implements Iterator,
ArrayPermutationsIter
{
private int [] Value;
private int N;
private long permutationCounter;
private boolean endWasReached = false;
private boolean wasNextValueCalculatedAlready = false;
/**
* Will hold the current value. Will be changed only by getNext()
*/
private int [] currentValueBackup;
/**
* Creates an array of size N with elements 1,2,...,n-1 Useful for
* describing regular permutations. See IntegerPermutationIter(int[] array)
* for the other kind of permutations; efficency of initiation is O(N)
*
* @param N
*/
public IntegerPermutationIter(int N)
{
int [] newArray = new int[N];
// fill the array with 1,2,3...
for (int i = 0; i < newArray.length; i++) {
newArray[i] = i;
}
init(newArray);
}
/**
* Uses a predefined array (sorted), for example:
* [3,1,1,2,1]-->[1,1,1,2,3]; note that there are much less than 5!
* premutations here, because of the repetitive 1s.
*
* @param array creates a copy of it (so sort / later changes will not
* matter)
*/
public IntegerPermutationIter(int [] array)
{
int [] newArray = new int[array.length];
System.arraycopy(array, 0, newArray, 0, array.length);
Arrays.sort(newArray);
init(newArray);
}
private void init(int [] array)
{
this.N = array.length;
this.Value = array;
this.currentValueBackup = this.Value;
permutationCounter = 0;
}
/**
* Swaps by array indexes
*
* @param i
* @param j
*/
private void swap(int i, int j)
{
int temp = this.Value[i];
this.Value[i] = this.Value[j];
this.Value[j] = temp;
}
private int [] arrayClone(int [] sourceArray)
{
int [] destArray = new int[sourceArray.length];
System.arraycopy(sourceArray, 0, destArray, 0, sourceArray.length);
return destArray;
}
private int [] getNextStartingWith2()
{
permutationCounter++;
int i = N - 1;
if (i <= 0) // may happen only on N<=1
{
this.endWasReached = true;
return null;
}
/** while (Value[i-1] >= Value[i])
{
i = i-1;
}*/
while (Value[i - 1] >= Value[i]) {
i = i - 1;
if (i == 0) {
this.endWasReached = true;
return null;
}
}
int j = N;
while (Value[j - 1] <= Value[i - 1]) {
j = j - 1;
}
swap(i - 1, j - 1); // swap values at positions (i-1) and (j-1)
i++;
j = N;
while (i < j) {
swap(i - 1, j - 1);
i++;
j--;
}
return this.Value;
}
/**
* Efficiency: O(N) implementation, try to take the next!
*/
@Override public boolean hasNext()
{
if ((this.permutationCounter == 0)
|| (this.wasNextValueCalculatedAlready))
{
return true;
} else if (this.endWasReached) {
return false;
}
boolean result = true;
// calculate the next value into this.value save the current result. in
// the end swap the arrays there is no way to know when to stop , but
// the out-of-bound
/* try
* {
* this.wasNextValueCalculatedAlready=true;
* getNextStartingWith2();
* }
* catch (ArrayIndexOutOfBoundsException outOfBoundException)
* {
* endWasReached=true;
* result=false;
* }*/
getNextStartingWith2();
this.wasNextValueCalculatedAlready = true;
if (endWasReached) {
return false;
}
//////////////////////////////
return result;
}
@Override public Object next()
{
return getNext();
}
/**
* Facade. use it with getNext. efficency: O(N)
*
* @return a new Array with the permutatation order. for example:
* perm0=[1,2,3,4] perm1=[1,2,4,3] perm2=[1,3,2,4]
*/
public int [] getNext()
{
if (!hasNext()) {
throw new RuntimeException(
"IntegerPermutationIter exceeds the total number of permutaions."
+ " Suggestion: do a check with hasNext() , or count till getTotalNumberOfPermutations"
+ " before using getNext()");
}
// if it is the first one , return original
int [] internalArray;
if (this.permutationCounter == 0) {
this.permutationCounter++;
internalArray = this.Value;
} else {
// if hasNext() has precaclulated it , take this value.
if (this.wasNextValueCalculatedAlready) {
internalArray = this.Value;
this.wasNextValueCalculatedAlready = false;
} else {
internalArray = getNextStartingWith2();
if (this.endWasReached) {
return null;
}
}
}
this.currentValueBackup = arrayClone(internalArray);
return arrayClone(internalArray);
}
public int [] getCurrent()
{
return arrayClone(this.currentValueBackup);
}
/**
* Utility method to convert the array into a string examples: [] [0]
* [0,1][1,0]
*
* @param array
*/
public String toString(int [] array)
{
if (array.length <= 0) {
return "[]";
}
StringBuffer stBuffer = new StringBuffer("[");
for (int i = 0; i < (array.length - 1); i++) {
stBuffer.append(array[i]).append(",");
}
stBuffer.append(array[array.length - 1]).append("]");
return stBuffer.toString();
}
/**
* UNIMPLEMENTED. always throws new UnsupportedOperationException
*
* @see java.util.Iterator#remove()
*/
@Override public void remove()
{
throw new UnsupportedOperationException();
}
/* (non-Javadoc)
* @see ArrayPermutationsIter#nextPermutation()
*/
@Override public int [] nextPermutation()
{
return (int []) next();
}
/* (non-Javadoc)
* @see ArrayPermutationsIter#hasNextPermutaions()
*/
@Override public boolean hasNextPermutaions()
{
return hasNext();
}
}
// End IntegerPermutationIter.java
