implement delete in Red-Black_Trees.cpp

Author: ashwek

3_Data_Structures/13_Red-Black_Trees/Red-Black_Trees.cpp

@@ -7,6 +7,8 @@ remains approximately balanced during insertions and deletions.
 https://en.wikipedia.org/wiki/Red%E2%80%93black_tree
 
 https://www.cs.usfca.edu/~galles/visualization/RedBlack.html
+
+http://www.cs.armstrong.edu/liang/animation/web/RBTree.html
 */
 
 #include <iostream>
@@ -162,6 +164,132 @@ class RBT{
  }
  }
 
+ Node *search(int value){
+
+ Node *tempNode = root;
+ while( tempNode != nill) {
+ if( tempNode->value == value ) return tempNode;
+ tempNode = (value <= tempNode->value) ? tempNode->left : tempNode->right;
+ }
+ return NULL;
+
+ }
+
+ void transplant(Node *node, Node *replacement){
+
+ if( node == root ) root = replacement;
+ else if( node->parent->left == node ) node->parent->left = replacement;
+ else node->parent->right = replacement;
+ replacement->parent = node->parent;
+
+ }
+
+ Node *successor(Node *node) {
+
+ if( node == NULL ) node = root;
+ if( node == NULL || node == nill ) return NULL;
+ if( node->right == nill ) {
+ while( node->parent != nill and node->parent->right == node )
+ node = node->parent;
+ return node->parent;
+ }
+
+ Node *tempNode = node->right;
+ while( tempNode->left != nill )
+ tempNode = tempNode->left;
+
+ return tempNode;
+
+ }
+
+ void delete_fix_up(Node *node){
+
+ Node *sibling;
+ while( node != root && node->node_color == BLACK){
+ if( node == node->parent->left){
+ sibling = node->parent->right;
+ if( sibling->node_color == RED){
+ sibling->node_color = BLACK;
+ node->parent->node_color = RED;
+ left_rotate(node->parent);
+ sibling = node->parent->right;
+ }
+
+ if( sibling->left->node_color == BLACK && sibling->right->node_color == BLACK){
+ sibling->node_color = RED;
+ node = node->parent;
+ }
+ else {
+ if( sibling->right->node_color == BLACK ){
+ sibling->left->node_color = BLACK;
+ sibling->node_color = RED;
+ right_rotate(sibling);
+ sibling = node->parent->right;
+ }
+ sibling->node_color = node->parent->node_color;
+ sibling->right->node_color = node->parent->node_color = BLACK;
+ left_rotate(node->parent);
+ node = root;
+ }
+ }
+ else {
+ sibling = node->parent->left;
+ if( sibling->node_color == RED){
+ sibling->node_color = BLACK;
+ node->parent->node_color = RED;
+ right_rotate(node->parent);
+ sibling = node->parent->left;
+ }
+
+ if( sibling->left->node_color == BLACK && sibling->right->node_color == BLACK){
+ sibling->node_color = RED;
+ node = node->parent;
+ }
+ else {
+ if( sibling->left->node_color == BLACK ){
+ sibling->right->node_color = BLACK;
+ sibling->node_color = RED;
+ left_rotate(sibling);
+ sibling = node->parent->left;
+ }
+ sibling->node_color = node->parent->node_color;
+ sibling->left->node_color = node->parent->node_color = BLACK;
+ right_rotate(node->parent);
+ node = root;
+ }
+ }
+ }
+ node->node_color = BLACK;
+ }
+
+ void remove(Node *node){
+
+ if( node == NULL || node == nill ) return;
+
+ colors delete_node_color = node->node_color;
+ Node *replacement;
+
+ if( node->left == nill ){
+ replacement = node->right;
+ transplant(node, replacement);
+ }
+ else if( node->right == nill ){
+ replacement = node->left;
+ transplant(node, replacement);
+ }
+ else {
+ Node *replacement = successor(node);
+ node->value = replacement->value;
+ remove(replacement);
+ return;
+ }
+
+ if( delete_node_color == BLACK ){
+ delete_fix_up(replacement);
+ }
+
+ }
+
 };
 
 int main(){
@@ -170,10 +298,25 @@ int main(){
  int temp;
  RBT a;
 
+ vector<int> nodes;
+
+ cout <<"\nInserting 10 nodes :";
  for(int i = 0; i < 10; i++) {
  temp = random() % 200 + 1;
- cout <<"\nInserting " <<temp;
+ cout <<"\n\tInserting " <<temp;
  a.insert(temp);
+ nodes.push_back(temp);
+ }
+
+ cout <<"\n\nInorder : ";
+ a.inorder();
+
+ cout <<"\n\nDeleting 5 nodes :";
+ while( nodes.size() > 5 ){
+ temp = random() % nodes.size();
+ cout << "\n\tDeleting : " <<nodes[temp];
+ a.remove(a.search(nodes[temp]));
+ nodes.erase(nodes.begin() + temp);
  }
 
  cout <<"\n\nInorder : ";