FIRST AND FOLLOW PROGRAM

/*CSEMATTER.BLOGSPOT.IN
PROGRAM-TO FIND FIRST AND FOLLOW*/

#include<stdio.h>
#include<ctype.h>
#include<string.h>
#include<conio.h>

void follow(char c);
void first_1(char c);
void FIRST(char );

int n,m=0,p,i=0,j=0;
char a[10][10],f[10];
int count,n1=0;
char  first[10];

int main()
{
 int i,z,choice;
 char c,ch;
 printf("Enter the no.of productions:");
 scanf("%d",&n);
 printf("Enter the productions(epsilon=$):\n");
 for(i=0;i<n;i++)
  scanf("%s%c",a[i],&ch);
count=n;

do
{
n1=0;
printf("Element :");
scanf("%c",&c);
FIRST(c);
printf("\n FIRST(%c)= { ",c);
for(i=0;i<n1;i++)
printf("%c ",first[i]);
printf("}\n");

printf("press 1 to continue : ");
scanf("%d%c",&choice,&ch);
}
while(choice==1);

 do
 {
  m=0;
  printf("Enter the element whose FOLLOW is to be found:");

  scanf("%c",&c);
  follow(c);
    printf("FOLLOW(%c) = { ",c);
  for(i=0;i<m;i++)
   printf("%c ",f[i]);
  printf(" }\n");
    printf("Do you want to continue(0/1)?");
  scanf("%d%c",&z,&ch);
 }
 while(z==1);
}

void follow(char c)
{

 if(a[0][0]==c)
 f[m++]='$';
 for(i=0;i<n;i++)
 {
  for(j=2;j<strlen(a[i]);j++)
  {
   if(a[i][j]==c)
   {
    if(a[i][j+1]!='\0')
     first_1(a[i][j+1]);

    if(a[i][j+1]=='\0'&&c!=a[i][0])
     follow(a[i][0]);

   }
  }
 }
}
void first_1(char c)
{
      int k;
                 if(!(isupper(c)))
                 f[m++]=c;

                 for(k=0;k<n;k++)
                 {
                 if(a[k][0]==c)
                 {
                 if(a[k][2]=='$')
                  follow(a[i][0]);
                 else if(islower(a[k][2]))
                 f[m++]=a[k][2];

                 else
                  first_1(a[k][2]);
                 }
                 }

}



void FIRST(char c)
{
int j;
if(!(isupper(c)))first[n1++]=c;
for(j=0;j<count;j++)
{
if(a[j][0]==c)
{
if(a[j][2]=='$') first[n1++]='$';
else if(islower(a[j][2]))first[n1++]=a[j][2];
else FIRST(a[j][2]);
}
}
}

/*OUTPUT

Enter the no.of productions:8
Enter the productions(epsilon=$):
E=TD
D=+TD
D=$
T=FS
S=*FS
S=$
F=(E)
F=a
Element :E
FIRST(E)= { ( a }
press 1 to continue : 1

Element :D
FIRST(D)= { + $ }
press 1 to continue : 1

Element :T
FIRST(T)= { ( a }
press 1 to continue : 1

Element :S
FIRST(S)= { * $ }
press 1 to continue : 1

Element :F
FIRST(F)= { ( a }
press 1 to continue : 0

Enter the element whose FOLLOW is to be found:E
FOLLOW(E) = { $ )  }
Do you want to continue(0/1)?1

Enter the element whose FOLLOW is to be found:D
FOLLOW(D) = { $ )  }
Do you want to continue(0/1)?1

Enter the element whose FOLLOW is to be found:T
FOLLOW(T) = { + $ )  }
Do you want to continue(0/1)?1

Enter the element whose FOLLOW is to be found:S
FOLLOW(S) = { + $ )  }
Do you want to continue(0/1)?1

Enter the element whose FOLLOW is to be found:F
FOLLOW(F) = { * + $ )  }
Do you want to continue(0/1)?0 */