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| CPP Program For Solve Regular Expression |
# include
# include
# include
# include
// regular expression to nfa by g.ram kumar
// works for everything but produces excessive epsilon transitions
int ret[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))
{ret[pos++]=sp;
ret[pos++]=*s;
ret[pos++]=++sc;}
if(*s=='.')
{sp=sc;
ret[pos++]=sc;
ret[pos++]=238;
ret[pos++]=++sc;
sp=sc;}
if(*s=='|')
{sp=st;
fs[fsc++]=sc;}
if(*s=='*')
{ret[pos++]=sc;
ret[pos++]=238;
ret[pos++]=sp;
ret[pos++]=sp;
ret[pos++]=238;
ret[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 %d\n",ret[i],ret[i+1],ret[i+2]);
printf("\n");
getch();
}
Sample Input and Output:
enter the regular expression :49+20
state input state
1 --ε--> 2
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