refactor rbt_delete_node

diff --git a/source/rbt/rbt.c b/source/rbt/rbt.c
index 764a83c3b1089c813fb24b0e1818c62eb9e56dcd..5c10c3b945d6d5aea99d3f57208170cb20edb382 100644 (file)
--- a/source/rbt/rbt.c
+++ b/source/rbt/rbt.c
@@ -203,35 +203,26 @@ static rbt_node_t* rightmost_descendent(rbt_node_t* node){
 }
 
 static void rbt_delete_node(rbt_t* tree, rbt_node_t* node){
-       rbt_node_t* parent = node->parent;
+       rbt_node_t* descendant = NULL;
        if(node->left && node->right){
-               rbt_node_t* replacement = rightmost_descendent(node->left);
-               mem_retain(replacement);
-               rbt_delete_node(tree, replacement);
-               if(node->left) node->left->parent = replacement;
-               if(node->right) node->right->parent = replacement;
-               replacement->left = node->left;
-               replacement->right = node->right;
-               replacement->color = node->color;
-               rbt_node_replace(tree, node, replacement);
-       }else{
-               //node has at most one non-leaf child
-               rbt_node_t* child = NULL;
-               if(RED == rbt_node_color(node)){
-                       //node cannot have children
-                       if(node == parent->left) parent->left = NULL;
-                       else parent->right = NULL;
-               } else if(RED == rbt_node_color(node->left) || RED == rbt_node_color(node->right)){
-                       child = node->left ? node->left : node->right;
-                       child->color = BLACK;
+               descendant = rightmost_descendent(node->left);
+               mem_retain(descendant);
+               rbt_delete_node(tree, descendant);
+               if(node->left) node->left->parent = descendant;
+               if(node->right) node->right->parent = descendant;
+               descendant->left = node->left;
+               descendant->right = node->right;
+               descendant->color = node->color;
+       }else if(BLACK == rbt_node_color(node)){
+               //black node with at most one non-leaf child
+               if(RED == rbt_node_color(node->left) || RED == rbt_node_color(node->right)){
+                       descendant = node->left ? node->left : node->right;
+                       descendant->color = BLACK;
                } else {
                        rbt_del_rebalance(tree, node);
-                       //reset child/parent after rebalance; tree may have been rotated
-                       parent = node->parent;
-                       child = node->left ? node->left : node->right;
                }
-               rbt_node_replace(tree, node, child);
        }
+       rbt_node_replace(tree, node, descendant);
        node->left = NULL;
        node->right = NULL;
        node->parent = NULL;