tsearch(3C)															       tsearch(3C)

NAME

       tsearch(), tfind(), tdelete(), twalk() - manage binary search trees

SYNOPSIS

DESCRIPTION

       and  are  routines  for manipulating binary search trees.  They are generalized from Knuth (6.2.2) Algorithms T and D.  All comparisons are
       done with a user-supplied routine, compar.  This routine is called with two arguments, the pointers to the  elements  being  compared.	It
       returns	an integer less than, equal to, or greater than 0, according to whether the first argument is to be considered less than, equal to
       or greater than the second argument.  The comparison function need not compare every byte, so arbitrary data may be contained in  the  ele-
       ments in addition to the values being compared.

       is  used  to  build and access the tree.  key is a pointer to an entry to be accessed or stored.  If there is an entry in the tree equal to
       the value pointed to by key, a pointer to the previous key associated with this found entry is returned.  Otherwise, key is inserted, and a
       pointer	to  it	returned.   Note  that	since  the value returned is a pointer to key and key itself is a pointer, the value returned is a
       pointer to a pointer.  Only pointers are copied, so the calling routine must store the data.  rootp points to a variable that points to the
       root  of  the tree.  A NULL value for the variable pointed to by rootp denotes an empty tree; in this case, the variable is set to point to
       the entry which will be at the root of the new tree.

       Like searches for an entry in the tree, returning a pointer to it if found.  However, if it is not found,  returns  a  NULL  pointer.   The
       arguments for are the same as for

       deletes	a  node  from a binary search tree.  Arguments are the same as for The variable pointed to by rootp is changed if the deleted node
       was the root of the tree.  returns a pointer to the parent of the deleted node, or a NULL pointer if the node is not found.

       traverses a binary search tree.	root is the root of the tree to be traversed.  (Any node in a tree may be used as  the	root  for  a  walk
       below that node.)  action is the name of a routine to be invoked at each node.  This routine is, in turn, called with three arguments:

	      o  First argument is the address of the node being visited.

	      o  Second  argument  is  a value from an enumeration data type (defined in the header file), depending on whether this is the first,
		 second or third time that the node has been visited (during a depth-first, left-to-right traversal of the tree), or  whether  the
		 node is a leaf.

	      o  Third argument is the level of the node in the tree, with the root being level zero.

EXAMPLES

       The  following  code reads strings, and stores structures containing a pointer to each string and a count of its length.  It then walks the
       tree, printing out the stored strings and their lengths in alphabetical order.

RETURN VALUE

       A NULL pointer is returned by if there is not enough space available to create a new node.

       A NULL pointer is returned by and if rootp is NULL on entry.

       If the datum is found, both and return a pointer to it.	If not, returns NULL, and returns a pointer to the inserted item.

WARNINGS

       The root argument to is one level of indirection less than the rootp arguments to and

       Two nomenclatures are used to refer to the order in which tree nodes are visited.  uses preorder, postorder and	endorder  to  respectively
       refer  to visiting a node before any of its children, after its left child and before its right and after both its children.  The alternate
       nomenclature uses preorder, inorder, and postorder to refer to the same visits, which could result in some confusion over  the  meaning	of
       postorder.  If the calling function alters the pointer to the root, results are unpredictable.

SEE ALSO

       bsearch(3C), hsearch(3C), lsearch(3C), thread_safety(5).

STANDARDS CONFORMANCE

																       tsearch(3C)