NAME
tsearch, tfind, tdelete, twalk —
manipulate binary search
trees
SYNOPSIS
#include
<search.h>
void *
tdelete(const
void * restrict key, void
** restrict rootp, int
(*compar) (const void *, const void *));
void *
tfind(const
void *key, const void *
const *rootp, int
(*compar) (const void *, const void *));
void *
tsearch(const
void *key, void
**rootp, int (*compar)
(const void *, const void *));
void
twalk(const
void *root, void
(*action) (const void *, VISIT, int));
DESCRIPTION
Thetdelete(),
tfind(), tsearch(), and
twalk() functions manage binary search trees based on
algorithms T and D from Knuth (6.2.2). The comparison function passed in by
the user has the same style of return values as
strcmp(3).
tfind()
searches for the datum matched by the argument key in
the binary tree rooted at rootp, returning a pointer
to the datum if it is found and NULL if it is not.
tsearch()
is identical to tfind() except that if no match is
found, key is inserted into the tree and a pointer to
it is returned. If rootp points to a NULL value a new
binary search tree is created.
tdelete()
deletes a node from the specified binary search tree and returns a pointer
to the parent of the node to be deleted. It takes the same arguments as
tfind() and tsearch(). If
the node to be deleted is the root of the binary search tree,
rootp will be adjusted.
twalk()
walks the binary search tree rooted in root and calls
the function action on each node.
Action is called with three arguments: a pointer to
the current node, a value from the enum
typedef enum
{ preorder, postorder, endorder, leaf } VISIT; specifying the
traversal type, and a node level (where level zero is the root of the
tree).
RETURN VALUES
The tsearch() function returns NULL if
allocation of a new node fails (usually due to a lack of free memory).
tfind(),
tsearch(), and tdelete()
return NULL if rootp is NULL or the datum cannot be
found.
The twalk() function returns no value.
SEE ALSO
STANDARDS
These functions conform to IEEE Std 1003.1-2001 (“POSIX.1”).
CAVEATS
The IEEE Std 1003.1-2001
(“POSIX.1”) standard does not specify what value should
be returned when deleting the root node. Since implementations vary, user of
tdelete() should not rely on any specific behaviour.
The IEEE Std 1003.1-2008 (“POSIX.1”)
revision tried to clarify the issue with the following wording: “the
tdelete() function shall return a pointer to the
parent of the deleted node, or an unspecified non-NULL pointer if the
deleted node was the root node, or a NULL pointer if
the node is not found”.