C PROGRAM FOR BALANCED EXPRESSION

Consider the following I/O samples.

SAMPLE INPUT 1: [10+(6-2)/{3-1}]       

SAMPLE OUTPUT 1 :  VALID

      

SAMPLE INPUT 2: (([a-z]+{c-d}/a)-d)/n)

SAMPLE OUTPUT 1 :  INVALID

 

C PROGRAM:

#include <stdio.h>
#include <stdbool.h>
#include <string.h>
#define MAX_SIZE 100

int top=-1;
char arr[MAX_SIZE];
int isEmpty()
{
    if(top == -1)
        return true;
    else
        return false;
}

int isFull()
{
    if(top == MAX_SIZE-1)
        return true;
    else
        return false;
}

void push(char item)
{
    if(isFull())
        printf("Stack is full");
    else
        top++;
        arr[top] = item;
}

void pop()
{
    if(isEmpty())
        printf("Stack is empty");
    else
        top--;
}

char gettop()
{
    return arr[top];
}

int pair(char opening,char closing)
{
if(opening == '(' && closing == ')') 
    return true;
else if(opening == '{' && closing == '}') 
    return true;
else if(opening == '[' && closing == ']') 
    return true;
return false;
}

int main()
{
    char expr[MAX_SIZE];
    int length=0,i,j;
    scanf("%s",expr);
    length = strlen(expr);
    for(i=0;i<length;i++)
    {
        if(expr[i] == '(' || expr[i] == '{' || expr[i] == '[')
                push(expr[i]);
        else if(expr[i] == ')' || expr[i] == '}' || expr[i] == ']')
        {
            
            if(isEmpty() || !pair(gettop(),expr[i]))
            {
                printf("\nNOT BALANCED");
                return 0;
            }
            else
            {
                pop();
            }
        }
    }
    if(isEmpty())
        printf("\nBALANCED");
    else
        printf("\nNOT BALANCED");

}

 

OUTPUT:

 

  

The given source code in C program is short and simple to understand. The source code is well tested in DEV-C++ and is completely error free. 
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