Question

JAVA QUESTION - BalancedParentheses

Implement the class BalancedParentheses with a method isBalanced that receives a String and checks whether the brackets in it are balanced.

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) {

// INSERT YOUR CODE HERE

}

}

Answer 1

//AS THE QUESTION DEMANDS ONLY BALANCING OF PARENTHESES SO OTHER BRACKETS ARE NOT CONSIDERED//
/***********************CODE PROVIDED IN THE QUESTION START***********************/
import java.util.Scanner;
import java.util.Stack; //FOR USING STACK IN THE PROGRAM   
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");
}
/***********************CODE PROVIDED IN THE QUESTION END***********************/

/**********************************ADDED CODE***********************/
public static boolean isBalanced(String s)
{
Stack<Character> stack = new Stack<Character>();
char[] ch = s.toCharArray(); //CONVERT STRING TO CHARACTER ARRAY
//SELECTIVELY ADDING THE EXPRESSION TO STACK
//ONLY OPEN PARENTHESES ARE ADDED TO THE STACK
for (char c : ch)
{ //push() AND pop() ARE USED FOR PUSH AND POP ON STACK RESPECTIVELY
if(c == '(') //IF OPEN PARENTHESES IS ENCOUNTERED THEN PUSH IT TO STACK
stack.push(c);
else if (c== ')') //IF CLOSING PARENTHESES IS ENCOUNTERD THEN POP FROM STACK
{    //EACH CLOSING PARENTHESES POPS OUT CORESPONDING OPEN PARENTHESES
if(stack.isEmpty()) //IF CLOSING PARENTHESES IS ENCOUNTED BEFORE AN OPEN PARENTHESES
return false; //THAT IS STACK IS EMPTY AND POP() FUNCTION IS GOING TO BE CALLED
stack.pop(); //THEN IT IS UNBALANCED USE OF PARENTHESES
}
}
return stack.isEmpty();   //isEmpty() RETURNS TRUE IF STACK IS EMPTY AND VICE VERSA
  
}
}