Ngx_rbtree_t red/black tree

: This article mainly introduces the ngx_rbtree_t red/black tree. if you are interested in the PHP Tutorial, refer to it. Ngx_rbtree_t red/black tree

Features of the red/black tree

1. The node is red or black;
2. The root node is black;
3. All leaf nodes are black (that is, NIL sentinel nodes );
4. The two subnodes of each red node are black;
5. All simple paths from any node to each of its leaf nodes contain the same number of black nodes.

Red/black tree node structure

Typedef ngx_uint_t regular; typedefstruct regular ngx_rbtree_node_t; structstruct ngx_rbtree_node_s {// unsigned integer keyword primary key; // left subnode Primary * left; // right subnode Primary * right; // parent node ngx_rbtree_node_t * parent; // node color, 0: black, 1: Red u_char color; // only one byte of data u_char data ;};

Place such a tree node in the first member of the element, which facilitates direct forced conversion.

I. e.

typedefstruct {    ngx_rbtree_node_t   node;    ngx_uint_t          num;    }TestRBTreeBode;

Functions provided by the red/black tree node

Function name	Parameter description	Meaning
Ngx_rbt_red (node)	Node is a node pointer of the ngx_rbtree_node_t type.	Set node to red
Ngx_rbt_black (node)	Node is a node pointer of the ngx_rbtree_node_t type.	Set node to black
Ngx_rbt_is_red (node)	Node is a node pointer of the ngx_rbtree_node_t type.	Judge whether the node is red
Ngx_rbt_is_black (node)	Node is a node pointer of the ngx_rbtree_node_t type.	Judge whether the node is black
Ngx_rbt_copy_color (n1, n2)	N1 and n2 are the same as above	Copy the node color of n2 to n1
Ngx_rbtree_node_t * ngx_rbtree_min (node, sentinel)	Node and sentinel are of the ngx_rbtree_node_t * type.	Find the minimum node in the current node and its subtree (by key)
Ngx_rbtree_sentinel_init (node)	Same as node	Initialize the sentinel node

Red/black tree structure

Typedefstruct ngx_rbtree_s ngx_rbtree_t;/* pointer */typedefvoid (* cursor) (ngx_rbtree_node_t * root, ngx_rbtree_node_t * node to solve element conflicts with the same keywords on different nodes, optional * sentinel); struct ngx_rbtree_s {// point to the root node of the tree (which can be directly converted to a data element) ngx_rbtree_node_t * root; // point to NIL sentinel node ngx_rbtree_node_t * sentinel; // ngx_rbtree_insert_pt insert ;};

Functions provided by the red/black tree container

Function name	Parameter description	Meaning
Ngx_rbtree_init (tree, s, I)	Tree is the container pointer; s is the Sentinel pointer; I is the addition function of the ngx_rbtree_insert_pt type.	Initialize the red/black tree
Void ngx_rbtree_insert (ngx_rbtree_t * tree, ngx_rbtree_node_t * node)	Tree is the same as above; node is the added node pointer	Add nodes to automatically rotate and maintain nodes
Void ngx_rbtree_delete (ngx_rbtree_t * tree, ngx_rbtree_node_t * node)	Tree is the same as above; node is the node pointer to be deleted	Delete a node and automatically rotate and maintain the node.

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