148 lines
2.9 KiB
Plaintext
148 lines
2.9 KiB
Plaintext
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.TH AVL 2
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.SH NAME
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mkavltree, insertavl, lookupavl, deleteavl, avlwalk, avlnext, avlprev, endwalk - AVL tree routines
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.SH SYNOPSIS
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.\" .ta 0.75i 1.5i 2.25i 3i 3.75i 4.5i
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.ta 0.7i +0.7i +0.7i +0.7i +0.7i +0.7i +0.7i
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.EX
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#include <u.h>
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#include <libc.h>
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#include <avl.h>
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.sp 0.3v
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typedef struct Avl Avl;
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struct Avl
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{
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Avl *p; /* parent */
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Avl *n[2]; /* children */
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int bal; /* balance bits */
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};
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.sp 0.3v
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Avl *avlnext(Avlwalk *walk);
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Avl *avlprev(Avlwalk *walk);
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Avlwalk *avlwalk(Avltree *tree);
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void deleteavl(Avltree *tree, Avl *key, Avl **oldp);
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void endwalk(Avlwalk *walk);
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void insertavl(Avltree *tree, Avl *new, Avl **oldp);
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Avl *lookupavl(Avltree *tree, Avl *key);
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Avl *searchavl(Avltree *tree, Avl *key, int neighbor);
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Avltree *mkavltree(int(*cmp)(Avl*, Avl*));
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.EE
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.SH DESCRIPTION
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An AVL tree is a self-balancing binary search tree.
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These routines allow creation and maintenance of in-memory AVL trees.
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.PP
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An empty AVL tree is created by calling
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.I mkavltree
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with a comparison function as argument.
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This function should take two pointers to
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.B Avl
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objects and return -1, 0 or 1 as the first is
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respectively less than,
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equal to, or greater than,
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the second.
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.I Insertavl
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adds a
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.I new
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tree node into
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.IR tree .
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If
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.I oldp
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is non-nil upon return,
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it points to storage for an old node
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with the same key that may now be freed.
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.I Lookupavl
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returns the
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.I tree
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node that matches
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.I key
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by
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.IR tree 's
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comparison function,
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or
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.B nil
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if none.
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.PP
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.I Searchavl
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returns the
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.I tree
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node that matches
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.I key
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by
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.IR tree 's
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comparison function, if it exists.
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If it does not, and
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.I neighbor
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is positive, it returns the nearest node whose
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.I key
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is greater or
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.B nil
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if there is none and, if
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.I neighbor
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is negative, it returns the nearest node whose
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.I key
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is less or
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.B nil
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if there is none.
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It is an error to set
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.I neighbor
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to values other than \-1, 0, or +1.
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.PP
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.I Deleteavl
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removes the node matching
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.I key
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from
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.IR tree ;
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.I oldp
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is handled as per
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.IR insertavl .
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.PP
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.I Avlwalk
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returns a pointer to a newly-allocated
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.B Avlwalk
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object.
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.I Endwalk
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frees such an object.
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.I Avlnext
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and
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.I avlprev
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walk the tree associated with
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.IR walk ,
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returning the next
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(respectively, previous)
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tree node in the comparison order
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defined by the comparison function
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associated with the tree associated with
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.IR walk .
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.SH EXAMPLES
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Intended usage seems to be to make an anonymous
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.B Avl
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the first member of the application's tree-node structure,
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then pass these routines tree-node pointers instead of
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.BR Avl* s.
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.IP
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.EX
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typedef struct Node {
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Avl;
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uchar score[VtScoreSize];
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int type;
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} Node;
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.sp 0.3v
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Avltree *tree;
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Avl *res;
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Node *np;
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\fI\&...\fP
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res = lookupavl(tree, np);
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.EE
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.SH SOURCE
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.B /sys/src/libavl
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.SH SEE ALSO
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G. M. Adelson-Velsky,
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E. M. Landis,
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``An algorithm for the organization of information'',
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.IR "Soviet Mathematics" ,
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Vol. 3, pp. 1256—1263.
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.SH DIAGNOSTICS
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Functions returning pointers return
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.B nil
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on error.
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