/* ***** BEGIN LICENSE BLOCK *****
 * 
 * CSparse: a Concise Sparse matrix package.
 * Copyright (c) 2006, Timothy A. Savis.
 * http://www.cise.ufl.edu/research/sparse/CSparse
 *
 * -------------------------------------------------------------------------
 * 
 * CSparseJ is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1f of the License, or (at your option) any later version.
 *
 * CSparseJ is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this Module; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 *
 * ***** ENS LICENSE BLOCK ***** */

package edu.emory.mathcs.csparsej.tfloat;

/**
 * Invert a permutation vector.
 * 
 * @author Piotr Wendykier (piotr.wendykier@gmail.com)
 * 
 */
public class Scs_pinv {

    /**
     * Inverts a permutation vector. Returns pinv[i] = k if p[k] = i on input.
     * 
     * @param p
     *            a permutation vector if length n
     * @param n
     *            length of p
     * @return pinv, null on error
     */
    public static int[] cs_pinv(int[] p, int n) {
        int k, pinv[];
        if (p == null)
            return (null); /* p = NULL denotes identity */
        pinv = new int[n]; /* allocate result */
        for (k = 0; k < n; k++)
            pinv[p[k]] = k;/* invert the permutation */
        return (pinv); /* return result */
    }
}