SP1_W3

import java.io.BufferedReader;
import java.io.IOException;
import java.io.StringReader;
import java.util.Scanner;
public class BalancedParentheses {
    public static void main(String[] args) {
        checkParentheses("((a + b) * t/2 * (1 - t)");
        checkParentheses("(a + b) * t)/(2 * (1 - t)");
        checkParentheses("a + ((a + b) * t)/(2 * (1 - t))");
        System.out.println("Enter an expression: ");
        Scanner scanner = new Scanner(System.in);
        String s = scanner.nextLine();
        checkParentheses(s);
    }
    public static void checkParentheses(String s) {
        System.out.println(s + " is "
                + (isBalanced(s) ? "" : "not ")
                + "parentheses balanced");
    }
    public static boolean isBalanced(String s) {
        BufferedReader br = new BufferedReader(new StringReader(s));
        int level = 0;
        int charInt;

        try {
            while ((charInt = br.read()) != -1) {
                char c = (char) charInt;
                if (c == '(') {
                    level++;
                } else if (c == ')') {
                    level--;
                }

                if (level < 0) {
                    return false;
                }
            }

            return level == 0;
        } catch (IOException e) {
            System.out.println(e.getMessage());
            return false;
        }
    }
}