#include <stdio.h>
#include <stdlib.h>

struct node {
	char data;
	struct node * prev_top;
};

void push( struct node ** curr_top_ref , char data )
{
	struct node * temp_node = ( struct node * )malloc( sizeof( struct node ));
	
	if( temp_node != NULL )
	{
		temp_node->data = data;
		temp_node->prev_top = *curr_top_ref;
		*curr_top_ref = temp_node;
	}
}

void pop( struct node ** curr_top_ref )
{
	struct node * top;
	if( curr_top_ref != NULL )
	{
		top = *curr_top_ref;
		*curr_top_ref = top->prev_top;
		free(top);
	}
}


int isbracketbalanced( char expr[] )
{
	struct node * curr_stack_top = NULL;
	int i = 0;
	
	while(expr[i])
	{
		if( expr[i]=='(' || expr[i] == '{' || expr[i] == '[' )
		{
			push( &curr_stack_top , expr[i] );
		}
		
		if( curr_stack_top == NULL )
		{
			return 0;
		}
		
		switch(expr[i])
		{
			case ')':
				if( curr_stack_top-> data == '(' )
					pop( &curr_stack_top);
				else
					return 0;
				break;
			case '}':
				if( curr_stack_top-> data == '{' )
					pop( &curr_stack_top);
				else
					return 0;
				break;
			case ']':
				if( curr_stack_top-> data == '[' )
					pop( &curr_stack_top);
				else
					return 0;
				break;			
		}
		i++;
	}
	
	if( curr_stack_top == NULL )
	{
		return 1;
	}
	else
	{
		return 0;
	}
}

int main(void) {
	// your code goes here
	char test1[] = "{[]}";
	if( isbracketbalanced(test1))
		printf("brackets are balanced \n");
	else
		printf("brackets are not balanced \n");
	
	return 0;
}