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