C program for converting regular expression to NFA

C program to convert regular expression to NFA:

To convert the regular expression to NFA, this method is known as the Subset method.

The steps in this method are given below:-

Step-1: Make a transition diagram for a given regular expression, using NFA with ε moves.

Step-2: Then, Convert this NFA with ε to NFA without ε.

Step-3: Finally, Convert the obtained NFA to an equivalent DFA.

#include
#include
#include
#include
int r[100];
static int pos = 0;
static int sc = 0;
void nfa(int st, int p, char*s)
{
int i,sp,fs[15],fsc=0;
sp=st:pos=p;sc=st;
while(*s!=NULL)
{
if(isalpha(*s))
{
r[pos++]=sp;
r[pos++]=*s;
r[pos++]=++sc;}
if(*s=='.')
{
sp=sc;
r[pos++]=sc;
r[pos++]=238;
r[pos++]=++sc;
sp=sc;
}
if(*s=='|')
{
sp=st;
fs[fsc++]=sc;
}
if(*s=='*')
{
r[pos++]=sc;
r[pos++]=238;
r[pos++]=sp;
r[pos++]=sp;
r[pos++]=238;
r[pos++]=sc;
}
if(*s=='(')
{
char ps[50];
int i=0,flag=1;
s++;
while(flag!=0)
{
ps[i++]=*s;
if(*s=='(')
flag++;
if(*s==')')
flag--;
s++;
}
ps[--i]='\0';
nfa(sc,pos,ps);
s--;
}
s++;
}
sc++;
for(i=0;i<fsc;i++)
{
r[pos++]=fs[i];
r[pos++]=238;
r[pos++]=sc;
}
r[pos++]=sc-1;
r[pos++]=238;
r[pos++]=sc;
}
void main()
{
int i;
char *inp;
clrscr();
printf("enter the regular expression :");
gets(inp);
nfa(1,0,inp);
printf("\nstate input state\n");
for(i=0;i<pos;i=i+3) print("%d --%c--> %d\n", r[i], r[i+1], r[i+2]);
printf("\n");
getch();
}