Balancing of BST.cpp

BST/cpp/Balancing of BST.cpp

@@ -0,0 +1,105 @@
+/* C++ program to convert a left unbalanced BST to a balanced BST */
+#include <bits/stdc++.h> 
+using namespace std; 
+
+struct Node 
+{ 
+	int data; 
+	Node* left, *right; 
+}; 
+
+/* This function traverse the skewed binary tree and 
+stores its nodes pointers in vector nodes[] */
+void storeBSTNodes(Node* root, vector<Node*> &nodes) 
+{ 
+	// Base case 
+	if (root==NULL) 
+		return; 
+
+	// Store nodes in Inorder (which is sorted 
+	// order for BST) 
+	storeBSTNodes(root->left, nodes); 
+	nodes.push_back(root); 
+	storeBSTNodes(root->right, nodes); 
+} 
+
+/* Recursive function to construct binary tree */
+Node* buildTreeUtil(vector<Node*> &nodes, int start, 
+				int end) 
+{ 
+	// base case 
+	if (start > end) 
+		return NULL; 
+
+	/* Get the middle element and make it root */
+	int mid = (start + end)/2; 
+	Node *root = nodes[mid]; 
+
+	/* Using index in Inorder traversal, construct 
+	left and right subtress */
+	root->left = buildTreeUtil(nodes, start, mid-1); 
+	root->right = buildTreeUtil(nodes, mid+1, end); 
+
+	return root; 
+} 
+
+// This functions converts an unbalanced BST to 
+// a balanced BST 
+Node* buildTree(Node* root) 
+{ 
+	// Store nodes of given BST in sorted order 
+	vector<Node *> nodes; 
+	storeBSTNodes(root, nodes); 
+
+	// Constucts BST from nodes[] 
+	int n = nodes.size(); 
+	return buildTreeUtil(nodes, 0, n-1); 
+} 
+
+// Utility function to create a new node 
+Node* newNode(int data) 
+{ 
+	Node* node = new Node; 
+	node->data = data; 
+	node->left = node->right = NULL; 
+	return (node); 
+} 
+
+/* Function to do preorder traversal of tree */
+void preOrder(Node* node) 
+{ 
+	if (node == NULL) 
+		return; 
+	printf("%d ", node->data); 
+	preOrder(node->left); 
+	preOrder(node->right); 
+} 
+
+// Driver program 
+int main() 
+{ 
+	/* Constructed skewed binary tree is 
+				10 
+			/ 
+			8 
+			/ 
+			7 
+		/ 
+		6 
+		/ 
+		5 */
+
+	Node* root = newNode(10); 
+	root->left = newNode(8); 
+	root->left->left = newNode(7); 
+	root->left->left->left = newNode(6); 
+	root->left->left->left->left = newNode(5); 
+
+	root = buildTree(root); 
+
+	printf("Preorder traversal of balanced "
+			"BST is : \n"); 
+	preOrder(root); 
+
+	return 0; 
+}