Task-2

class Node:
    def __init__(self, data):
        self.data = data
        self.next = None


class Stack:

    # Constructor
    def __init__(self):
        self.top = 0
        self.head = None

    # Adds element to the Stack
    def push(self, data):
        self.top += 1
        if self.head == None:
            self.head = Node(data)
        else:
            newNode = Node(data)
            newNode.next = self.head
            self.head = newNode

    # Removes element from the stack
    def pop(self):
        if self.head == None:
            return "Stack Empty!"
        else:
            self.top -= 1
            item = self.head.data
            self.head = self.head.next
            return item

    # Returns the peek element of the stack
    def peek(self):
        if self.head == None:
            return "Stack Empty!"
        else:
            item = self.head.data
            return item

    # Checks if the stack is empty or not
    def is_empty(self):
        if self.head == None:
            return True
        else:
            return False

    def size(self):
        return self.top

class CheckBalancedBracket:
    def is_balanced(self, expression):
        print(expression)
        stack = Stack()
        indexes = Stack()
        dict = {')': '(', '}': '{', ']': '['}
        index = 0
        for c in expression:
            index += 1
            if c == ')' or c == '}' or c == ']':
                if dict[c] != stack.peek():
                    print("This expression is NOT correct.")
                    if indexes.peek() != "Stack Empty!":
                        print(f"Error at character #{indexes.peek()}. '{stack.peek()}' - not closed.")
                    else:
                        print(f"Error at character #{index}. '{c}' - not opened.")
                    return
                else:
                    stack.pop()
                    indexes.pop()
            elif c == '(' or c == '[' or c == '{':
                stack.push(c)
                indexes.push(index)
        if stack.is_empty():
            print("This expression is correct.")
            return
        else:
            while stack.size() > 1:
                stack.pop()
                indexes.pop()
            print("This expression is NOT correct.")
            print(f"Error at character #{indexes.peek()}. '{stack.peek()}' - not closed.")
            return




arithmaticExpression = input("Enter the expression: ")
ans = CheckBalancedBracket()
ans.is_balanced(arithmaticExpression)