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#include "cs.h"
/* consider A(i,j), node j in ith row subtree and return lca(jprev,j) */
csi cs_leaf (csi i, csi j, const csi *first, csi *maxfirst, csi *prevleaf,
csi *ancestor, csi *jleaf)
{
csi 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) */
}
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