Question

Implement a program that will use a stack structure to check for correct placement of parentheses in an algebraic expression. Allow the use of ( ) [ ] { } characters as grouping symbols. Make sure that an error is reported for an expression of a form (...]. In addition report other possible parentheses related errors (too many levels, too many right paren., too many left paren.). Make sure to use 'silent error reporting' (and report any possible errors outside the main scanner loop).

Answer 1

Code:

import java.io.*;
import java.util.*;
import java.util.Stack;

public class CheckParentesis {

public static void main(String[] args) {
     Scanner sc=new Scanner(System.in);
     System.out.println("Enter string");
     String str=sc.next();
   
String booleanCheck=CheckingParenthesis(str);
System.out.println("String "+booleanCheck);
}
public static String CheckingParenthesis(String expr)
{
if (expr.isEmpty())
return "Balanced";

Stack<Character> stack = new Stack<Character>();
for (int i = 0; i < expr.length(); i++)
{
char current = expr.charAt(i);
if (current == '{' || current == '(' || current == '[')
{
stack.push(current);
}
if (current == '}' || current == ')' || current == ']')
{
if (stack.isEmpty())
return "is having too many right parentheses";
char last = stack.peek();
if (current == '}' && last == '{' || current == ')' && last == '(' || current == ']' && last == '[')
stack.pop();

}
}
return stack.isEmpty()?" Balanced":"is having too many left parentheses";
}

}

Output:

Output JavaApplication37 (debug) x Debugger Console x Debugger Console x JavaApplication37 (run) x Enter string String was Balanced BUILD SUCCESSFUL (total time : 2 seconds)

Output ル Debugger Console x Debugger Console x Dx avaApplication37 (un) x Enter string CO String is having too many left parentheses BUILD SUCCESSFUL (total time: 2 seconds)

Output Debugger Console x Debugger Console x JavaApplication37 (run) x ル! run Enter string String is having too many right parentheses BUILD SUCCESSFUL (total time: 5 seconds)