Balanced Binary Trees: GLib Reference Manual

## Balanced Binary Trees Balanced Binary Trees — a sorted collection of key/value pairs optimized for searching and traversing in order |

## Functions

GTree * | g_tree_new ()
GTree * | g_tree_ref ()
void | g_tree_unref ()
GTree * | g_tree_new_with_data ()
GTree * | g_tree_new_full ()
void | g_tree_insert ()
void | g_tree_replace ()
gint | g_tree_nnodes ()
gint | g_tree_height ()
gpointer | g_tree_lookup ()
gboolean | g_tree_lookup_extended ()
void | g_tree_foreach ()
void | g_tree_traverse ()
gboolean | (*GTraverseFunc) ()
gpointer | g_tree_search ()
gboolean | g_tree_remove ()
gboolean | g_tree_steal ()
void | g_tree_destroy ()

## Types and Values

| GTree

## Includes

    #include <glib.h>

## Description

The GTree structure and its associated functions provide a sorted collection of key/value pairs optimized for searching and traversing in order.

To create a new GTree use `g_tree_new()`.

To insert a key/value pair into a GTree use `g_tree_insert()`.

To lookup the value corresponding to a given key, use `g_tree_lookup()` and `g_tree_lookup_extended()`.

To find out the number of nodes in a GTree, use `g_tree_nnodes()`. To get the height of a GTree, use `g_tree_height()`.

To traverse a GTree, calling a function for each node visited in the traversal, use `g_tree_foreach()`.

To remove a key/value pair use `g_tree_remove()`.

To destroy a GTree, use `g_tree_destroy()`.

## Functions

### g_tree_new ()

    GTree *
    g_tree_new (GCompareFunc key_compare_func);

Creates a new GTree.

#### Parameters

key_compare_func | the function used to order the nodes in the GTree. It should return values similar to the standard `strcmp()` function - 0 if the two arguments are equal, a negative value if the first argument comes before the second, or a positive value if the first argument comes after the second. |

#### Returns

a newly allocated GTree

### g_tree_ref ()

    GTree *
    g_tree_ref (GTree *tree);

Increments the reference count of `tree` by one.

It is safe to call this function from any thread.

#### Parameters

tree | a GTree |

#### Returns

the passed in GTree

Since: 2.22

### g_tree_unref ()

    void
    g_tree_unref (GTree *tree);

Decrements the reference count of `tree` by one. If the reference count drops to 0, all keys and values will be destroyed (if destroy functions were specified) and all memory allocated by `tree` will be released.

It is safe to call this function from any thread.

#### Parameters

tree | a GTree |

Since: 2.22

### g_tree_new_with_data ()

    GTree *
    g_tree_new_with_data (GCompareDataFunc key_compare_func,
                          gpointer key_compare_data);

Creates a new GTree with a comparison function that accepts user data. See `g_tree_new()` for more details.

#### Parameters

key_compare_func | qsort()-style comparison function |
key_compare_data | data to pass to comparison function |

#### Returns

a newly allocated GTree

### g_tree_new_full ()

    GTree *
    g_tree_new_full (GCompareDataFunc key_compare_func,
                     gpointer key_compare_data,
                     GDestroyNotify key_destroy_func,
                     GDestroyNotify value_destroy_func);

Creates a new GTree like `g_tree_new()` and allows to specify functions to free the memory allocated for the key and value that get called when removing the entry from the GTree.

#### Parameters

key_compare_func | qsort()-style comparison function |
key_compare_data | data to pass to comparison function |
key_destroy_func | a function to free the memory allocated for the key used when removing the entry from the GTree or `NULL` if you don't want to supply such a function |
value_destroy_func | a function to free the memory allocated for the value used when removing the entry from the GTree or `NULL` if you don't want to supply such a function |

#### Returns

a newly allocated GTree

### g_tree_insert ()

    void
    g_tree_insert (GTree *tree,
                   gpointer key,
                   gpointer value);

Inserts a key/value pair into a GTree.

If the given key already exists in the GTree its corresponding value is set to the new value. If you supplied a `value_destroy_func` when creating the GTree, the old value is freed using that function. If you supplied a `key_destroy_func` when creating the GTree, the passed key is freed using that function.

The tree is automatically 'balanced' as new key/value pairs are added, so that the distance from the root to every leaf is as small as possible.

#### Parameters

tree | a GTree |
key | the key to insert |
value | the value corresponding to the key |

### g_tree_replace ()

    void
    g_tree_replace (GTree *tree,
                    gpointer key,
                    gpointer value);

Inserts a new key and value into a GTree similar to `g_tree_insert()`. The difference is that if the key already exists in the GTree, it gets replaced by the new key. If you supplied a `value_destroy_func` when creating the GTree, the old value is freed using that function. If you supplied a `key_destroy_func` when creating the GTree, the old key is freed using that function.

The tree is automatically 'balanced' as new key/value pairs are added, so that the distance from the root to every leaf is as small as possible.

#### Parameters

tree | a GTree |
key | the key to insert |
value | the value corresponding to the key |

### g_tree_nnodes ()

    gint
    g_tree_nnodes (GTree *tree);

Gets the number of nodes in a GTree.

#### Parameters

tree | a GTree |

#### Returns

the number of nodes in `tree`

### g_tree_height ()

    gint
    g_tree_height (GTree *tree);

Gets the height of a GTree.

If the GTree contains no nodes, the height is 0. If the GTree contains only one root node the height is 1. If the root node has children the height is 2, etc.

#### Parameters

tree | a GTree |

#### Returns

the height of `tree`

### g_tree_lookup ()

    gpointer
    g_tree_lookup (GTree *tree,
                   gconstpointer key);

Gets the value corresponding to the given key. Since a GTree is automatically balanced as key/value pairs are added, key lookup is O(log n) (where n is the number of key/value pairs in the tree).

#### Parameters

tree | a GTree |
key | the key to look up |

#### Returns

the value corresponding to the key, or `NULL` if the key was not found

### g_tree_lookup_extended ()

    gboolean
    g_tree_lookup_extended (GTree *tree,
                            gconstpointer lookup_key,
                            gpointer *orig_key,
                            gpointer *value);

Looks up a key in the GTree, returning the original key and the associated value. This is useful if you need to free the memory allocated for the original key, for example before calling `g_tree_remove()`.

#### Parameters

tree | a GTree |
lookup_key | the key to look up |
orig_key | returns the original key |
value | returns the value associated with the key |

#### Returns

`TRUE` if the key was found in the GTree

### g_tree_foreach ()

    void
    g_tree_foreach (GTree *tree,
                    GTraverseFunc func,
                    gpointer user_data);

Calls the given function for each of the key/value pairs in the GTree. The function is passed the key and value of each pair, and the given `data` parameter. The tree is traversed in sorted order.

The tree may not be modified while iterating over it (you can't add/remove items). To remove all items matching a predicate, you need to add each item to a list in your GTraverseFunc as you walk over the tree, then walk the list and remove each item.

#### Parameters

tree | a GTree |
func | the function to call for each node visited. If this function returns `TRUE`, the traversal is stopped. |
user_data | user data to pass to the function |

### g_tree_traverse ()

    void
    g_tree_traverse (GTree *tree,
                     GTraverseFunc traverse_func,
                     GTraverseType traverse_type,
                     gpointer user_data);

`g_tree_traverse` has been deprecated since version 2.2 and should not be used in newly-written code.

The order of a balanced tree is somewhat arbitrary. If you just want to visit all nodes in sorted order, use `g_tree_foreach()` instead. If you really need to visit nodes in a different order, consider using an n-ary tree.

Calls the given function for each node in the GTree.

#### Parameters

tree | a GTree |
traverse_func | the function to call for each node visited. If this function returns `TRUE`, the traversal is stopped. |
traverse_type | the order in which nodes are visited, one of `G_IN_ORDER`, `G_PRE_ORDER` and `G_POST_ORDER` |
user_data | user data to pass to the function |

### GTraverseFunc ()

    gboolean
    (*GTraverseFunc) (gpointer key,
                      gpointer value,
                      gpointer data);

Specifies the type of function passed to `g_tree_traverse()`. It is passed the key and value of each node, together with the `user_data` parameter passed to `g_tree_traverse()`. If the function returns `TRUE`, the traversal is stopped.

#### Parameters

key | a key of a GTree node |
value | the value corresponding to the key |
data | user data passed to `g_tree_traverse()` |

#### Returns

`TRUE` to stop the traversal

### g_tree_search ()

    gpointer
    g_tree_search (GTree *tree,
                   GCompareFunc search_func,
                   gconstpointer user_data);

Searches a GTree using `search_func` .

The `search_func` is called with a pointer to the key of a key/value pair in the tree, and the passed in `user_data` . If `search_func` returns 0 for a key/value pair, then the corresponding value is returned as the result of `g_tree_search()`. If `search_func` returns -1, searching will proceed among the key/value pairs that have a smaller key; if `search_func` returns 1, searching will proceed among the key/value pairs that have a larger key.

#### Parameters

tree | a GTree |
search_func | a function used to search the GTree |
user_data | the data passed as the second argument to `search_func` |

#### Returns

the value corresponding to the found key, or `NULL` if the key was not found

### g_tree_remove ()

    gboolean
    g_tree_remove (GTree *tree,
                   gconstpointer key);

Removes a key/value pair from a GTree.

If the GTree was created using `g_tree_new_full()`, the key and value are freed using the supplied destroy functions, otherwise you have to make sure that any dynamically allocated values are freed yourself. If the key does not exist in the GTree, the function does nothing.

#### Parameters

tree | a GTree |
key | the key to remove |

#### Returns

`TRUE` if the key was found (prior to 2.8, this function returned nothing)

### g_tree_steal ()

    gboolean
    g_tree_steal (GTree *tree,
                  gconstpointer key);

Removes a key and its associated value from a GTree without calling the key and value destroy functions.

If the key does not exist in the GTree, the function does nothing.

#### Parameters

tree | a GTree |
key | the key to remove |

#### Returns

`TRUE` if the key was found (prior to 2.8, this function returned nothing)

### g_tree_destroy ()

    void
    g_tree_destroy (GTree *tree);

Removes all keys and values from the GTree and decreases its reference count by one. If keys and/or values are dynamically allocated, you should either free them first or create the GTree using `g_tree_new_full()`. In the latter case the destroy functions you supplied will be called on all keys and values before destroying the GTree.

#### Parameters

tree | a GTree |

## Types and Values

### GTree

    typedef struct _GTree GTree;

The GTree struct is an opaque data structure representing a balanced binary tree. It should be accessed only by using the following functions.