TSEARCH(3) | Library Functions Manual | TSEARCH(3)

# 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

bsearch(3), lsearch(3)

# 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.

March 31, 2022 | Debian