/*
 * CXSPARSE: a Concise Sparse Matrix package - Extended.
 * Copyright (c) 2006-2009, Timothy A. Davis.
 * http://www.cise.ufl.edu/research/sparse/CXSparse
 * 
 * CXSparse 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 2.1 of the License, or (at your option) any later version.
 * 
 * CXSparse 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
 */

#include "cs.h"
/* consider A(i,j), node j in ith row subtree and return lca(jprev,j) */
CS_INT cs_leaf (CS_INT i, CS_INT j, const CS_INT *first, CS_INT *maxfirst, CS_INT *prevleaf,
    CS_INT *ancestor, CS_INT *jleaf)
{
    CS_INT q, s, sparent, jprev ;
    if (!first || !maxfirst || !prevleaf || !ancestor || !jleaf) return (-1) ;
    *jleaf = 0 ;
    if (i <= j || first [j] <= maxfirst [i]) return (-1) ;  /* j not a leaf */
    maxfirst [i] = first [j] ;      /* update max first[j] seen so far */
    jprev = prevleaf [i] ;          /* jprev = previous leaf of ith subtree */
    prevleaf [i] = j ;
    *jleaf = (jprev == -1) ? 1: 2 ; /* j is first or subsequent leaf */
    if (*jleaf == 1) return (i) ;   /* if 1st leaf, q = root of ith subtree */
    for (q = jprev ; q != ancestor [q] ; q = ancestor [q]) ;
    for (s = jprev ; s != q ; s = sparent)
    {
        sparent = ancestor [s] ;    /* path compression */
        ancestor [s] = q ;
    }
    return (q) ;                    /* q = least common ancester (jprev,j) */
}