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TSEARCH(3)	       FreeBSD Library Functions Manual		    TSEARCH(3)

     tsearch, tfind, tdelete, twalk -- manipulate binary search	trees

     #include <search.h>

     void *
     tdelete(const void	* restrict key,	posix_tnode ** restrict	rootp,
	 int (*compar) (const void *, const void *));

     posix_tnode *
     tfind(const void *key, posix_tnode	* const	*rootp,
	 int (*compar) (const void *, const void *));

     posix_tnode *
     tsearch(const void	*key, posix_tnode **rootp,
	 int (*compar) (const void *, const void *));

     twalk(const posix_tnode *root,
	 void (*action)	(const posix_tnode *, VISIT, int));

     The tdelete(), tfind(), tsearch(),	and twalk() functions manage binary
     search trees.  This implementation	uses a balanced	AVL tree, which	due to
     its strong	theoretical limit on the height	of the tree has	the advantage
     of	calling	the comparison function	relatively infrequently.

     The comparison function passed in by the user has the same	style of re-
     turn values as strcmp(3).

     The tfind() function 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.

     The tsearch() function 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.

     The tdelete() function 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.

     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; specify-
     ing the traversal type, and a node	level (where level zero	is the root of
     the tree).

     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 datum cannot be found.

     The twalk() function returns no value.

     This example uses tsearch() to search for four strings in root.  Because
     the strings are not already present, they are added.  tsearch() is	called
     twice on the fourth string	to demonstrate that a string is	not added when
     it	is already present.  tfind() is	used to	find the single	instance of
     the fourth	string,	and tdelete() removes it.  Finally, twalk() is used to
     return and	display	the resulting binary search tree.

     #include <stdio.h>
     #include <search.h>
     #include <string.h>

     comp(const	void *a, const void *b)

	     return strcmp(a, b);

     printwalk(const posix_tnode * node, VISIT v, int __unused0)

	     if	(v == postorder	|| v ==	leaf) {
		     printf("node: %s\n", *(char **)node);

	     posix_tnode *root = NULL;

	     char one[]	= "blah1";
	     char two[]	= "blah-2";
	     char three[] = "blah-3";
	     char four[] = "blah-4";

	     tsearch(one, &root, comp);
	     tsearch(two, &root, comp);
	     tsearch(three, &root, comp);
	     tsearch(four, &root, comp);
	     tsearch(four, &root, comp);
	     printf("four: %s\n", *(char **)tfind(four,	&root, comp));
	     tdelete(four, &root, comp);

	     twalk(root, printwalk);
	     return 0;

     bsearch(3), hsearch(3), lsearch(3)

     These functions conform to	IEEE Std 1003.1-2008 ("POSIX.1").

     The posix_tnode type is not part of IEEE Std 1003.1-2008 ("POSIX.1"), but
     is	expected to be standardized by future versions of the standard.	 It is
     defined as	void for source-level compatibility.  Using posix_tnode	makes
     distinguishing between nodes and keys easier.

FreeBSD	13.0			 June 4, 2017			  FreeBSD 13.0


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