refactor del_rebalance

diff --git a/source/rbt/rbt.c b/source/rbt/rbt.c
index 9cc96a43cf5137419a3430ea4641ca389c6a4938..b3d533eb4699b3b08d68f37a818cfb60faf80d22 100644 (file)
--- a/source/rbt/rbt.c
+++ b/source/rbt/rbt.c
@@ -151,42 +151,32 @@ rbt_node_t* rbt_lookup(rbt_t* tree, void* value){
 static void rbt_del_rebalance(rbt_t* tree, rbt_node_t* node){
        rbt_node_t* parent = node->parent;
        if(parent){
-               rbt_node_t* sib = (node == parent->left ? parent->right : parent->left);
+               direction_t node_side = (node == parent->left ? LEFT : RIGHT);
+               rbt_node_t* sib = (node_side == LEFT ? parent->right : parent->left);
+               rbt_node_t* inside_nibling = sib ? (node_side == LEFT ? sib->left : sib->right) : NULL;
+               rbt_node_t* outside_nibling = sib ? (node_side == LEFT ? sib->right : sib->left) : NULL;
                if(RED == node_color(sib)){
-                       //if sibbling is red, rotate to make sibbling black
-                       if(node == parent->left) rotate(tree, parent, LEFT);
-                       else rotate(tree, parent, RIGHT);
+                       //rotate so sib is black & recurse w/ new scenario
+                       rotate(tree, parent, node_side);
                        parent->color = RED;
                        sib->color = BLACK;
-                       //recurse with new sibbling / parent
                        rbt_del_rebalance(tree, node);
-               }else if(BLACK == node_color(sib->left) && BLACK == node_color(sib->right)){
+               }else if(BLACK == node_color(inside_nibling) && BLACK == node_color(outside_nibling)){
+                       //both niblings are black ; can paint sib red & rebalance on parent
                        sib->color = RED;
                        if(RED == node_color(parent)) parent->color = BLACK;
-                       //recurse to balance parent
                        else rbt_del_rebalance(tree, parent);
-               }else if(node == parent->left && BLACK == node_color(sib->right)){
-                       //convert "inside" case to "outside" case
-                       sib->left->color = BLACK;
-                       sib->color = RED;
-                       rotate(tree, sib, RIGHT);
-                       rbt_del_rebalance(tree, node);
-               }else if(node == parent->left && RED == node_color(sib->right)){
-                       rotate(tree, parent, LEFT);
-                       sib->color = parent->color;
-                       parent->color = BLACK;
-                       sib->right->color = BLACK;
-               }else if(node == parent->right && BLACK == node_color(sib->left)){
-                       //convert "inside" case to "outside" case
-                       sib->right->color = BLACK;
+               }else if(BLACK == node_color(outside_nibling)){
+                       //convert "inside" case to "outside" case & recurse w/ new scenario
+                       rotate(tree, sib, (node_side == LEFT ? RIGHT : LEFT));
                        sib->color = RED;
-                       rotate(tree, sib, LEFT);
+                       inside_nibling->color = BLACK;
                        rbt_del_rebalance(tree, node);
                }else{
-                       rotate(tree, parent, RIGHT);
+                       rotate(tree, parent, node_side);
                        sib->color = parent->color;
                        parent->color = BLACK;
-                       sib->left->color = BLACK;
+                       outside_nibling->color = BLACK;
                }
        }else{
                node->color = BLACK; //TODO: verify this is necessary