| TSEARCH(3) | Library Functions Manual | TSEARCH(3) |
tdelete, tfind,
tsearch, twalk —
manipulate binary search trees
#include
<search.h>
void *
tdelete(const void *restrict
key, void **restrict rootp, int
(*compar) (const void *key1, const void *key2));
void *
tfind(const void *key,
void *const *rootp, int (*compar)
(const void *key1, const void *key2));
void *
tsearch(const void *key,
void **rootp, int (*compar) (const
void *key1, const void *key2));
void
twalk(const void *root,
void (*action) (const void *node, VISIT order, int
level));
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 takes two arguments, each of which is a key pointer. This
function has the same style of return values as
strcmp(3).
The
tfind()
function searches for a node whose key matches the argument
key in the binary tree rooted at
rootp, returning a pointer to the node if it is found
and NULL if it is not.
Note that a node is itself a pointer to the key of the node. Thus, you should generally cast this result to a double pointer to the data type stored in the tree, for example (struct myType **), and use double indirection to retrieve the original key value.
The
tsearch()
function is identical to tfind() except that, if no
match is found, it inserts a new node for the key into
the tree and returns a pointer to the node. If rootp
points to a NULL value, a new binary search tree is created.
The
tdelete()
function deletes a node from the specified binary search tree and returns a
pointer to the parent of the node that was 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.
The
twalk()
function walks the binary search tree rooted in root
and calls the function action on each node. The
action function 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).
As
twalk()
traverses the tree, it calls the action function with
the traversal type "preorder" before visiting the left subtree of
the node, with the traversal type
"postorder" before visiting the right subtree of the
node, and with the traversal type "endorder"
after visiting the right subtree of the node.
The action function is called only once for a leaf-node, with the traversal type "leaf."
Note: the names for the traversal types differ somewhat from common parlance. The traversal type "postorder" corresponds to what would typically be referred to as in-order, and the traversal type "endorder" corresponds to what would typically be referred to as post-order.
The tsearch() function returns NULL if
allocation of a new node fails (usually due to a lack of free memory).
The tfind(),
tsearch(), and tdelete()
functions return NULL if rootp is NULL or the node
cannot be found.
The twalk() function returns no value.
| June 15, 1997 | macOS 15.0 |