NAME
tsearch, tfind,
tdelete, twalk —
manipulate binary search
trees
SYNOPSIS
#include
<search.h>
void *
tdelete(const
void *key, void
**rootp, int
(*compar)(const void *, const void *));
void *
tfind(const
void *key, 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
The
tdelete(),
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. If the node to be deleted is the
root of the binary search tree, rootp will be adjusted
and an unspecified non-null pointer will be returned. It takes the same
arguments as tfind() and
tsearch().
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).
tdelete() returns a pointer to the parent
of the deleted node or an unspecified non-null pointer if the root node is
deleted.
tfind(),
tsearch(), and tdelete()
return NULL if rootp is
NULL or the datum cannot be found.
SEE ALSO
STANDARDS
These functions conform to IEEE Std 1003.1-2008 (“POSIX.1”).
CAVEATS
The value returned when deleting the root node was unspecified
before the IEEE Std 1003.1-2008
(“POSIX.1”) standard, so users of the
tdelete() function should be wary of relying on a
specific behaviour.