Question

Using java language. Build an expression tree. • When you see a number: o you create a new node with the number as the data. o Then you push the new node to the stack. . When you see a binary operator: 0 You create a new Node for the operator. Then you pop and set the right child. Then you pop and set the left child o Then you push the new node to the stack. At the end of the expression you will have just one item on the stack. You can set this to be the root of the binary tree. Now you have your expression on the tree.

Test Data would be as follows:

Answer 1

// Java program to construct an expression tree

import java.util.Stack;

// Java program for expression tree

class Node {

    char value;

    Node left, right;

    Node(char item) {

        value = item;

        left = right = null;

    }

}

class ExpressionTree {

    // A utility function to check if 'c'

    // is an operator

    boolean isOperator(char c) {

        if (c == '+' || c == '-'

                || c == '*' || c == '/'

                || c == '^') {

            return true;

        }

        return false;

    }

    // Utility function to do inorder traversal

    void inorder(Node t) {

        if (t != null) {

            inorder(t.left);

            System.out.print(t.value + " ");

            inorder(t.right);

        }

    }

    // Returns root of constructed tree for given

    // postfix expression

    Node constructTree(char postfix[]) {

        Stack<Node> st = new Stack();

        Node t, t1, t2;

        // Traverse through every character of

        // input expression

        for (int i = 0; i < postfix.length; i++) {

            // If operand, simply push into stack

            if (!isOperator(postfix[i])) {

                t = new Node(postfix[i]);

                st.push(t);

            } else // operator

            {

                t = new Node(postfix[i]);

                // Pop two top nodes

                // Store top

                t1 = st.pop();      // Remove top

                t2 = st.pop();

                // make them children

                t.right = t1;

                t.left = t2;

                // System.out.println(t1 + "" + t2);

                // Add this subexpression to stack

                st.push(t);

            }

        }

        // only element will be root of expression

        // tree

        t = st.peek();

        st.pop();

        return t;

    }

    public static void main(String args[]) {

        ExpressionTree et = new ExpressionTree();

        String postfix = "76%3@#/$";

        char[] charArray = postfix.toCharArray();

        Node root = et.constructTree(charArray);

        System.out.println("infix expression is");

        et.inorder(root);

    }

}