Red black tree implemented in Dart (#3009)

Red_Black_Tree/Red_Black_Tree.dart

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+/**
+ *   Red Black Tree
+ * -------------------------------
+ * RB Tree is a self balancing tree which is of O(logn) time complexity
+ * for various operations. It has 4 balancing rules as follows:
+ * 
+ * 1. Nodes are of either red or black color.
+ * 2. Root is always black.
+ * 3. Red node should not have red children
+ * 4. Every path from a node (including root) to any of its descendant 
+ * NULL node has the same number of black nodes.
+ * 
+ */
+
+// Importing required libraries
+import 'dart:io';
+
+// Defining colors as constants to increase readability and decrease confusion
+const bool BLACK = false;
+const bool RED = true;
+
+// Class definition of a node
+class Node{
+    int value;
+    bool color;
+    Node parent, left, right;
+
+    Node(int value){
+        this.value = value;
+        this.color = RED;
+    }
+}
+
+// Class definition of a RB Tree
+class RBTree{
+
+    // Tree's root
+    Node root;
+
+    // Utility function to print a RB Tree
+    void printRBTree(Node root){
+        if(root != null){
+            print(root.value);
+            printRBTree(root.left);
+            printRBTree(root.right);
+        }
+    }
+
+    // Utility method to search in the tree
+    Node searchRBTree(Node root, int target){
+        if(root == null){
+            return null;
+        }
+        if(root.value == target){
+            return root;
+        }
+        else if(root.value < target){
+            return searchRBTree(root.right, target);
+        }
+        else{
+            return searchRBTree(root.left, target);
+        }
+    }
+
+    // Utility method to perform BST insertion
+    Node insertBST(Node root, Node node){
+        if(root == null){
+            root = node; 
+        }
+        else{
+            if(root.value < node.value){
+                root.right = insertBST(root.right, node);
+                root.right.parent = root;
+            }
+            else if(root.value > node.value){
+                root.left = insertBST(root.left, node);
+                root.left.parent = root;
+            }
+        }
+        return root;
+    }
+
+    // Utility method for left rotation
+    Node rotateLeft(Node root, Node node){
+
+        Node node_right = node.right;
+        node.right = node_right.left;
+        if(node.right != null){
+            node.right.parent = node;
+        }
+        node_right.parent = node.parent;
+        if(node.parent == null){
+            root = node_right;
+        }
+        else if(node == node.parent.left){
+            node.parent.left = node_right;
+        }
+        else{
+            node.parent.right = node_right;
+        }
+        node_right.left = node;
+        node.parent = node_right;
+        return root;
+
+    }
+
+    // Utility method for right rotation
+    Node rotateRight(Node root,Node node){
+
+        Node node_left = node.left;
+        node.left = node_left.right;
+
+        if(node.left != null){
+            node.left.parent = node;
+        }
+
+        node_left.parent = node.parent;
+
+        if(node.parent == null){
+            root = node_left;
+        }
+        else if(node == node.parent.left){
+            node.parent.left = node_left;
+        }
+        else{
+            node.parent.right = node_left;
+        }
+
+        node_left.right = node;
+        node.parent = node_left;
+        return root;
+    }
+
+    // Utility method to swap colors of two nodes
+    void swapColor(Node node1, Node node2){
+        if(node1 == null || node2 == null){
+            return;
+        }
+        bool temp;
+        temp = node1.color;
+        node1.color = node2.color;
+        node2.color = temp;
+    }
+
+    // Utility method to fix violation of rules of RB Tree
+    Node fixViolation(Node root, Node node){
+        Node parentnode = null;
+        Node grandparent = null;
+        while((node != root) && (node.color != BLACK) && (node.parent.color == RED)){
+            parentnode = node.parent;
+            grandparent = node.parent.parent;
+            if(parentnode == grandparent.left){
+                Node uncle = grandparent.right;
+                if(uncle != null && uncle.color == RED){
+                    grandparent.color = RED;
+                    parentnode.color = BLACK;
+                    uncle.color = BLACK;
+                    node = grandparent;
+                }
+                else{
+                    if(node == parentnode.right){
+                        root = rotateLeft(root,parentnode);
+                        node = parentnode;
+                        parentnode = node.parent;
+                        grandparent = parentnode.parent;
+                    }
+                    root = rotateRight(root, grandparent);
+                    swapColor(parentnode,grandparent);
+                    node = parentnode;
+                }
+            }
+            else{
+                Node uncle = grandparent.left;
+
+                if((uncle != null) && (uncle.color == RED)){
+                    grandparent.color = RED;
+                    parentnode.color = BLACK;
+                    uncle.color = BLACK;
+                    node = grandparent;
+                }
+                else{
+                    if(node == parentnode.left){
+                        root = rotateRight(root,parentnode);
+                        node = parentnode;
+                        parentnode = node.parent;
+                        grandparent = parentnode.parent;
+                    }
+                    root = rotateLeft(root,grandparent);
+                    swapColor(parentnode,grandparent);
+                    node = parentnode;
+                }
+            }
+
+        }
+        root.color = BLACK;
+        return root;
+    }
+
+    // Method to insert into RB Tree
+    Node insertRBT(Node root, int value){
+        Node node = Node(value);
+        root = insertBST(root, node);
+        root = fixViolation(root, node);
+        return root;
+    }
+
+}
+
+// Driver method of the program
+void main(){
+
+    // Initialization of the tree
+    RBTree tree = RBTree();
+    int continued = 1;
+
+    while(continued == 1){
+        print("Enter 1 to insert, 2 to search and 3 to print the tree:");
+        var input = stdin.readLineSync();
+        int option = int.parse(input);
+        switch(option){
+            case 1:
+                input = stdin.readLineSync();
+                int value = int.parse(input);
+                tree.root = tree.insertRBT(tree.root, value);
+                break;
+            case 2:
+                input = stdin.readLineSync();
+                int value = int.parse(input);
+                Node node1 = tree.searchRBTree(tree.root, value);
+                if(node1 == null){
+                    print("Value not found");
+                }
+                else{
+                    print("Value found!");
+                }
+                break;
+            case 3:
+                tree.printRBTree(tree.root);
+                break;
+            default:
+                break;
+        }
+        print("Enter 1 to continue:");
+        input = stdin.readLineSync();
+        continued = int.parse(input);
+    }   
+}
+
+/**
+ *   Sample Input and Output
+ * -----------------------------------
+ * Enter 1 to insert, 2 to search and 3 to print the tree:
+ * 1
+ * 7
+ * Enter 1 to continue:
+ * 1
+ * Enter 1 to insert, 2 to search and 3 to print the tree:
+ * 1
+ * 3
+ * Enter 1 to continue:
+ * 1
+ * Enter 1 to insert, 2 to search and 3 to print the tree:
+ * 1
+ * 18
+ * Enter 1 to continue:
+ * 1
+ * Enter 1 to insert, 2 to search and 3 to print the tree:
+ * 1
+ * 10
+ * Enter 1 to continue:
+ * 1
+ * Enter 1 to insert, 2 to search and 3 to print the tree:
+ * 1
+ * 22
+ * Enter 1 to continue:
+ * 1
+ * Enter 1 to insert, 2 to search and 3 to print the tree:
+ * 1
+ * 8
+ * Enter 1 to continue:
+ * 1
+ * Enter 1 to insert, 2 to search and 3 to print the tree:
+ * 1
+ * 11
+ * Enter 1 to continue:
+ * 1
+ * Enter 1 to insert, 2 to search and 3 to print the tree:
+ * 1
+ * 26
+ * Enter 1 to continue:
+ * 1
+ * Enter 1 to insert, 2 to search and 3 to print the tree:
+ * 3
+ * 7
+ * 3
+ * 18
+ * 10
+ * 8
+ * 11
+ * 22
+ * 26
+ * Enter 1 to continue:
+ * 1
+ * Enter 1 to insert, 2 to search and 3 to print the tree:
+ * 2
+ * 18
+ * Value found!!
+ * Enter 1 to continue:
+ * 1
+ * Enter 1 to insert, 2 to search and 3 to print the tree:
+ * 2
+ * 112
+ * Value not found!!
+ * Enter 1 to continue:
+ * 1
+ * Enter 1 to insert, 2 to search and 3 to print the tree:
+ * 1
+ * 2
+ * Enter 1 to continue:
+ * 1
+ * Enter 1 to insert, 2 to search and 3 to print the tree:
+ * 1
+ * 6
+ * Enter 1 to continue:
+ * 1
+ * Enter 1 to insert, 2 to search and 3 to print the tree:
+ * 1
+ * 13
+ * Enter 1 to continue:
+ * 1
+ * Enter 1 to insert, 2 to search and 3 to print the tree:
+ * 3
+ * 10
+ * 7
+ * 3
+ * 2
+ * 6
+ * 8
+ * 18
+ * 11
+ * 13
+ * 22
+ * 26
+ * Enter 1 to continue:
+ * 2
+ */