Linked List : Given a pointer to any node, delete the node pointed by the pointer

Given a linked list like this,

Given a pointer to any node, delete the node pointed by the pointer. Note: no head pointer is given.

Solution:

Assume a pointer to p3, lets call it to 'p'. Since only pointer to current node is provided, there is no way to delete the current node from the list. But instead of deleting the current node, we can just move the next node data to current node and delete the next node. The algorithm can be explained simply as,

Cheers!!
Jack

Trace path of a node in a BINARY TREE in Java

The problem is simple. Given a node, we should be able to show the path from the root to that node in a BINARY TREE (NOT A BINARY SEARCH TREE). This solution would help us how to traverse through a binary tree. Here I am going to do an inorder traversal. More on traversals on a binary tree can be found here.
Consider the following binary tree, we can see the path to be found and the node supplied to find it. We will be provided with a tree, its root and the node to be found.

76 is the item that we need to find. Although the example looks like a BINARY SEARCH TREE, we are not going to use the binary search tree way to find 76. So, we would have no other way than doing either of inorder, post-order or pre-order traversals. 

To attack this problem,we maintain a stack. The stack will always maintain the path. Whenever we encounter the node to be found, we will stop our process and the path in the current stack will give the path to be found. The solution for this problem shown would be : 43,887,46,78,76

I was having problem in returning from the recursive method in a proper manner. Thanks to the help of stackoverflow.com  and its code gurus, I was redirected to the right path.

Now, for the Java code part,

package dsa.tree;

import java.util.Stack;

public class TracePath {
 private Node n1;
 private Stack<Node> mainStack = null;
 
 public static void main(String args[]){
  TracePath nodeFinder = new TracePath();
  nodeFinder.find();
 }
 
 public void find(){
  Tree t = getSampleTree();
  trace(t,n1);
  for(Node iNode:mainStack){
   System.out.println(iNode.data);
  }
 }

 private Tree getSampleTree() {
  Tree bsTree = new BinarySearchTree();
  int randomData[] = {43,887,11,3,8,33,6,0,46,32,78,76,334,45};
  for(int i=0;i<randomData.length;i++){
   bsTree.add(randomData[i]);
  }
  n1 = bsTree.search(76);
  return bsTree;
 }
 
 public Stack<Node> trace(Tree t, Node node){
  mainStack = new Stack<Node>();
  trace(t.getRoot(),node);
  return mainStack;
 }
 
 private boolean trace(Node parent, Node node){
  mainStack.push(parent);
  if(node.equals(parent)){
   return true;
  }
  if(parent.left != null){
   if (trace(parent.left, node))
    return true;
  }
  if(parent.right!=null){
   if (trace(parent.right, node))
    return true;
  }
  mainStack.pop();
  return false;
 }
}

Binary Trees in Java

One of the coolest data structures that is both highly efficient and very simple is a Binary Tree. Binary Tree is a data structure where a there will be a node having at most two child nodes.

Lets briefly define the concepts of a binary tree and lets take look at a working Java program in the future posts. Binary Tree has three pointers, one pointing to the left child, one pointing to the right child and one pointer to the parent. These are the terms we use with respect to a binary tree.

• Root - The uppermost node in a binary tree. The parent node is always null for a root or we can say Root does not have a parent.
• Child - A child is a sub-node to a parent node. A child can be either a left child or a right child
• Leaf - A node which does not have any right or left nodes to it.
• Node - constitutes to an element of a tree which has three pointers one to parent, one to right child and one to left child. And it has a place holder to store the data as well.
  

There are more jargons available with regard to a binary tree but as of now these terms are sufficient.

One of the most common misunderstanding that many have is to tell the definition of a "Binary search tree" when asked for a "Binary tree". They are not the same!!. Although we can say binary search tree is a form of binary tree with some condition. All Binary search trees are Binary trees and not vice versa!!!!

If asked to write a binary tree structure in Java, the following code would be more than sufficient. Note: This is just a raw structure.

public class BinaryTree{
 
 class Node {
  Node left;
  Node right;
  Node parent;
  int data;
 }
 
 private Node root;

}

More trees to come in the following posts.
Cheers,
Bragaadeesh.