Balanced_Parentheses_Checker.cpp

#include <iostream>
using namespace std;

#define MAX 100
/*---------------------------------------------------------------------------*/
typedef struct stack{
    char elem[100];
    int top;
};
/*---------------------------------------------------------------------------*/
void push(stack *s, char item){
    if (s->top == MAX - 1){
        cout << "stack full";
    }
    else{
        s->top = s->top + 1;
        s->elem[s->top] = item;
    }
}
/*---------------------------------------------------------------------------*/
bool isempty(stack *s){
    if (s->top == -1)
        return true;
    else
        return false;
}
/*---------------------------------------------------------------------------*/
char pop(stack *s){
    if (s->top == -1){
        cout << "stack empty";
        return -1;
    }
    else{
        return s->elem[s->top--];
    }
}
/*---------------------------------------------------------------------------*/
// function to check if brackets are balanced
bool areBracketsBalanced(string expr){
    char x;
    stack s;
    s.top = -1;
    
    // Traversing the Expression
    for (int i = 0; i < expr.length(); i++){
        if (expr[i] == '(' || expr[i] == '[' || expr[i] == '{'){
            // Push the element in the stack
            push(&s, expr[i]);
        }
        
        // IF current current character is not opening bracket, then it must be closing. So stack cannot be empty at this point.
        if (isempty(&s))
            return false;
            
        switch (expr[i]){
            
            case ')':
                // Store the top element in a
                x = pop(&s);
                if (x == '{' || x == '[')
                    return false;
                break;
 
            case '}':
                // Store the top element in b
                x = pop(&s);
                if (x == '(' || x == '[')
                    return false;
                break;
 
            case ']':
                // Store the top element in c
                x = pop(&s);
                if (x == '(' || x == '{')
                    return false;
                break;
        }
    }  
    // Check Empty Stack
    return (isempty(&s));
}
/*---------------------------------------------------------------------------*/
// Driver code
int main(){
    string expr;
    cout << "Enter an expression : ";
    cin >> expr;
  
    // Function call
    if (areBracketsBalanced(expr))
        cout << "The Parentheses are Balanced in the given Expression \n";
    else
        cout << "The Parentheses are Not Balanced in the given Expression \n";
    return 0;
}

/* Sample inputs :
   {x^[(n(n+1))÷5n]/(2n+1)}
   {x^[(n(n+1))÷5n])/(2n+1))
   {x^[(n(n+1)]÷5n))/(2n+1})
 */

/*---------------------------------------------------------------------------*/