EXP5.cpp

#include <iostream>
#include <cstring>
#include <cctype> // For isalpha
using namespace std;

struct Node {
    char data;
    Node *left, *right;
    Node(char val) : data(val), left(nullptr), right(nullptr) {}
};

class Tree {
public:
    Node *root;
    Tree() : root(nullptr) {}

    void buildExpressionTree(const char *prefix) {
        Node *stack[50];
        int top = -1;

        for (int i = strlen(prefix) - 1; i >= 0; i--) {
            if (isalpha(prefix[i])) {
                stack[++top] = new Node(prefix[i]);
            } else {
                Node *node = new Node(prefix[i]);
                node->left = stack[top--];
                node->right = stack[top--];
                stack[++top] = node;
            }
        }
        root = stack[top];
    }

    void displayPostfix(Node *node) {
        if (!node) return;
        displayPostfix(node->left);
        displayPostfix(node->right);
        cout << node->data;
    }

    void deleteTree(Node *node) {
        if (!node) return;
        deleteTree(node->left);
        deleteTree(node->right);
        cout << "Deleting node: " << node->data << endl;
        delete node;
    }
};

int main() {
    Tree tree;
    char expression[50];
    int choice;

    do {
        cout << "1 -> Enter prefix expression\n";
        cout << "2 -> Display postfix expression\n";
        cout << "3 -> Delete tree\n";
        cout << "4 -> Exit\n";
        cout << "Choose an option (1-4): ";
        cin >> choice;

        switch (choice) {
            case 1:
                cout << "Enter the prefix expression (e.g., +--a*bc/def): ";
                cin >> expression;
                tree.buildExpressionTree(expression);
                break;
            case 2:
                if (tree.root) {
                    tree.displayPostfix(tree.root);
                    cout << endl;
                } else {
                    cout << "Tree is empty.\n";
                }
                break;
            case 3:
                if (tree.root) {
                    tree.deleteTree(tree.root);
                    tree.root = nullptr;
                } else {
                    cout << "Tree is already empty.\n";
                }
                break;
            case 4:
                cout << "\n// END OF CODE\n";
                break;
            default:
                cout << "Choose a valid option (1-4).\n";
        }
    } while (choice != 4);

    return 0;
}