Check nesting of parentheses using stack

/*

Write a program to check nesting of parentheses using stack

*/

#include<stdio.h>
#define MAX 30

int top=-1;
int stack[MAX];

void push(char);
char pop();

int match(char a,char b);

main()
{

char exp[MAX];
int valid;

printf("Enter an algebraic expression : ");

gets(exp);
valid=check(exp);

if(valid==1)
printf("Valid expression\n");
else
printf("Invalid expression\n");

}

int check(char exp[] )
{

int i;
char temp;

for(i=0;i<strlen(exp);i++)
{
if(exp[i]=='(' || exp[i]=='{' || exp[i]=='[')

push(exp[i]);

if(exp[i]==')' || exp[i]=='}' || exp[i]==']')

if(top==-1) /*stack empty*/

{
printf("Right parentheses are more than left parentheses\n");
return 0;
}
else
{
temp=pop();

if(!match(temp, exp[i]))
{
printf("Mismatched parentheses are : ");
printf("%c and %c\n",temp,exp[i]);
return 0;
}
}
}

if(top==-1) /*stack empty*/
{
printf("Balanced Parentheses\n");
return 1;
}
else
{
printf("Left parentheses more than right parentheses\n");
return 0;
}
}

int match(char a,char b)
{

if(a=='[' && b==']')
return 1;

if(a=='{' && b=='}')
return 1;

if(a=='(' && b==')')
return 1;

return 0;
}

void push(char item)
{
if(top==(MAX-1))
{
printf("Stack Overflow\n");
return;
}
top=top+1;
stack[top]=item;
}

char pop()
{
if(top==-1)
{
printf("Stack Underflow\n");
exit(1);
}
return(stack[top--]);
}