1 #include "cs.h"
2 /* consider A(i,j), node j in ith row subtree and return lca(jprev,j) */
cs_leaf(CS_INT i,CS_INT j,const CS_INT * first,CS_INT * maxfirst,CS_INT * prevleaf,CS_INT * ancestor,CS_INT * jleaf)3 CS_INT cs_leaf (CS_INT i, CS_INT j, const CS_INT *first, CS_INT *maxfirst, CS_INT *prevleaf,
4 CS_INT *ancestor, CS_INT *jleaf)
5 {
6 CS_INT q, s, sparent, jprev ;
7 if (!first || !maxfirst || !prevleaf || !ancestor || !jleaf) return (-1) ;
8 *jleaf = 0 ;
9 if (i <= j || first [j] <= maxfirst [i]) return (-1) ; /* j not a leaf */
10 maxfirst [i] = first [j] ; /* update max first[j] seen so far */
11 jprev = prevleaf [i] ; /* jprev = previous leaf of ith subtree */
12 prevleaf [i] = j ;
13 *jleaf = (jprev == -1) ? 1: 2 ; /* j is first or subsequent leaf */
14 if (*jleaf == 1) return (i) ; /* if 1st leaf, q = root of ith subtree */
15 for (q = jprev ; q != ancestor [q] ; q = ancestor [q]) ;
16 for (s = jprev ; s != q ; s = sparent)
17 {
18 sparent = ancestor [s] ; /* path compression */
19 ancestor [s] = q ;
20 }
21 return (q) ; /* q = least common ancester (jprev,j) */
22 }
23