👀 Views: 104 💬 Answers: 1 📅 Created: 2025-07-23

java algorithm data-structures Java

Quick question that's been bugging me - I'm learning this framework and I'm working on a personal project and I'm working with scenarios with my Binary Search Tree (BST) implementation in Java, specifically when trying to maintain balance after insertions. I've opted to implement an AVL tree to keep the height balanced, but I'm working with issues where the tree frequently rebalances, leading to suboptimal performance. The AVL rotations seem to be incorrectly applied, as I receive `java.lang.StackOverflowError` when inserting a sequence of elements that should ideally not necessitate multiple rebalances. Here's a simplified version of my insertion method: ```java class AVLTree { private class Node { int key, height; Node left, right; Node(int d) { key = d; height = 1; } } private Node root; int height(Node N) { if (N == null) return 0; return N.height; } int getBalance(Node N) { if (N == null) return 0; return height(N.left) - height(N.right); } Node rightRotate(Node y) { Node x = y.left; Node T2 = x.right; // Perform rotation x.right = y; y.left = T2; // Update heights y.height = Math.max(height(y.left), height(y.right)) + 1; x.height = Math.max(height(x.left), height(x.right)) + 1; // Return new root return x; } Node leftRotate(Node x) { Node y = x.right; Node T2 = y.left; // Perform rotation y.left = x; x.right = T2; // Update heights x.height = Math.max(height(x.left), height(x.right)) + 1; y.height = Math.max(height(y.left), height(y.right)) + 1; // Return new root return y; } Node insert(Node node, int key) { // Normal BST insertion if (node == null) return new Node(key); if (key < node.key) node.left = insert(node.left, key); else if (key > node.key) node.right = insert(node.right, key); else return node; // Duplicate keys are not allowed // Update height of this ancestor node node.height = 1 + Math.max(height(node.left), height(node.right)); // Get the balance factor int balance = getBalance(node); // If the node becomes unbalanced, then there are 4 cases if (balance > 1 && key < node.left.key) return rightRotate(node); if (balance < -1 && key > node.right.key) return leftRotate(node); if (balance > 1 && key > node.left.key) { node.left = leftRotate(node.left); return rightRotate(node); } if (balance < -1 && key < node.right.key) { node.right = rightRotate(node.right); return leftRotate(node); } return node; } } ``` I've tried to debug by printing the balance factors after each insertion, but they seem to fluctuate unexpectedly. I also verified that my rotations are not causing a loop, yet I still run into a stack overflow when inserting larger datasets. Any insights or suggestions on what I might be missing or how to better manage the balance after insertions would be greatly appreciated. This is part of a larger CLI tool I'm building. Any ideas what could be causing this? What am I doing wrong? Has anyone else encountered this?