Question

Write an efficient java program to implement BST. Your java program should read n words and its corresponding French and store it in a BST. Then read every English word and print its corresponding French by searching in BST. Assume your java program is in engtofren.java file

To compile: javac engtofren.java

To execute: java engtofren< any data file name

Your main method should be as follow:

public static void main(String args[]) {

engtofren bst = new engtofren (); //

try{

Scanner inf = new Scanner (System.in);                    

// Read input from KB/ File

// read no. of words

n = inf.nextInt();

for (i = 1; i <= n; i++){

     // read English word

     english = inf.next();

     // read corresponding word

     french = inf.next();

     bst.insert(english, french);

}

while(inf.hasNext()){

     // read next English word

     english = inf.next();

     search in BST and print its corresponding French if exist.

   }// end while

   inf.close();// close input file

}catch (Exception e) {prt("\nException " + e + "\n");}

}//

Read input from System.in. i.e. command prompt.

Sample data file can be as follow:

5 student etudiant book livre this cette is est a une this is a book

Answer 1

The algorithm to insert data into BST is:

1. Start from root.
2. If root is null create a new node and assign it to root. Else compare the inserting element with root, if less than root, then recurse for left, else recurse for right.
3. After reaching the end, just insert that node at left(if less than current) else right.

The algorithm to search is:

1. start from root.
2. first compare the key with root, if the key is present at root or root is null, return root.
3. If key is greater than root’s key, we recur for right subtree of root node. Otherwise we recur for left subtree.

The java code is as follows:

import java.util.Scanner;

public class engtofren
{
// Root of BST
   private Node root;
  
// Constructor
engtofren() {
root = null;
}
  
// This method mainly calls insertRecord()
void insert(String word, String meaning) {
root = insertRecord(root, word, meaning);
}
  
// A recursive function to insert a new key in BST
Node insertRecord(Node root, String word, String meaning) {
  
//   If the tree is empty, return a new node
if (root == null) {
root = new Node(word, meaning);
return root;
}
  
//   Otherwise, recur down the tree */
if (word.compareToIgnoreCase(root.word) < 0)
root.left = insertRecord(root.left, word, meaning);
else if (word.compareToIgnoreCase(root.word) > 0)
root.right = insertRecord(root.right, word, meaning);
  
//return the (unchanged) node pointer
return root;
}
  
   public Node search(Node root, String key)
   {
//   root is null or key is present at root
   if (root==null || root.word.equalsIgnoreCase(key))
{
       return root;
}
  
//   val is greater than root's key
   if (root.word.compareToIgnoreCase(key)>0)
   return search(root.left, key);
  
//   val is less than root's key
   return search(root.right, key);
   }
  
  
   public static void main(String args[]) {

       engtofren bst = new engtofren (); //

       try{

       Scanner inf = new Scanner (System.in);

// Read input from KB/ File

// read no. of words
       System.out.println("Enter no of words");
        int n = inf.nextInt();
        System.out.println("Enter words");

       for (int i = 1; i <= n; i++){

       // read English word

           String english = inf.next();

       // read corresponding word

       String french = inf.next();

       bst.insert(english, french);

       }

      
       while(inf.hasNext()){

//   read next English word
       String english = inf.next();

       Node searchedNode=bst.search( bst.root, english);
       System.out.println(searchedNode.word + " : " + searchedNode.meaning);
//   search in BST and print its corresponding French if exist.

       }

       inf.close();// close input file

       }catch (Exception e) {System.out.println("\nException " + e + "\n");}

       }
}

class Node
{
String word;
String meaning;
Node left, right;

public Node(String word, String meaning) {

this.word= word;
this.meaning=meaning;
left = right = null;
}
}