Parentheses Checker in C

Description

 This program is used to check balanced parentheses in an Expression.

#include
#define MAX 100
void input();
char stack[MAX];
int top = -1;

void push(char x)
{
 stack[++top]=x; 
}

char pop()
{
 if(top==-1)
 return 0;
 else
 return stack[top--];
}

main()
{
 int choice;
 do
 {
  printf("\n\n----MENU----\n");
  printf("1.Input expression\n2.EXIT\n");
  printf("\nEnter your choice\n");
  scanf("%d",&choice);
  switch(choice)
  {
   case 1:input();break;
   case 2:printf("\n~~~~Thank You~~~~\n");break;
   default:printf("\nINVALID INPUT !!!!\n");
  }
 }while(choice!=2);
}

void input()
{
 top=-1;
 int i=0,flag=1;
 char string[100],check;
 printf("Enter a parantheses string : ");
 scanf("%s",&string);
 while(string[i]!='\0')
 {
  if(string[i]=='('|| string[i]=='[' || string[i]=='{')
  push(string[i]);
  if(string[i]==')')
  {
   if(check=pop()!='(')
   {
    flag=0;break;
   }
  }
  if(string[i]==']')
  {
   if(check=pop()!='[')
   {
    flag=0;break;
   }
  }
  if(string[i]=='}')
  {
   if(check=pop()!='{')
   {
    flag=0;break;
   }
  }
  i++;
 }
 if(top!=-1 || flag == 0)
 printf("\nUNBALANCED parentheses expression !!!");
 else
 printf("\nBALANCED parentheses expression....");
}

---

OUTPUT

• Data Structure in C