TheAlgorithms-C/data_structures/stack/balanced parenthesis using stack in C

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define size 100

struct node
{
    char data;
    struct node* link;
};
int c=0;	// c used as counter to check if stack is empty or not
struct node * head;	 //declaring head pointer globally assigned to NULL

void push(char x) //function for pushing
{
struct node *p,*temp; 
    temp=(struct node*)malloc(sizeof(struct node));
    temp->data=x;
    if(head==NULL)	//will be execute only one time i.e, 1st time push is called
    {
        head=temp;
        p=head;
        p->link=NULL;
        c++;
    }
    else
    {
        temp->link=p;
        p=temp;
        head=p;
        c++;
    }
    
}
char pop(void)	//function for pop
{
    char x;
    struct node*p=head;
    x=p->data;
    head=p->link;
    free(p);
    c--;
    return x;
    
}

int isBalanced(char *s) {		   
    int i=0;char x;
 while(s[i]!='\0')	//loop for covering entire string of brackets
 {
     if(s[i]=='{'||s[i]=='('||s[i]=='[') //if opening bracket then push
         push(s[i]);
        else 
        {
            if(c<=0)			//i.e, stack is empty as only opening brackets are added to stack
                return 0;
        
            
               x=pop();			
                if( x=='{'&&s[i]!='}')	
                    return 0;
                if(x=='['&&s[i]!=']')
                    return 0;
                if(x=='('&&s[i]!=')')
                    return 0 ;
        }i++;       
    }			
      if(c==0)		//at end if stack is empy which means whole process has been performed correctly so retuen 1
          return 1;
        else
            return 0;
}

int main() {
    int t;
    scanf("%d",&t);
    for(int a0 = 0; a0 < t; a0++){
        char s[size];
int result;
        scanf("%s",s);
        result = isBalanced(s);
if(result==1)
printf("\nYES");
else       
 printf("\nNO");
		
    }
    return 0;
}