regextonfa.c

#include<stdio.h>
#include<malloc.h>
struct node
{
	int x;
	struct ptr *p;
	struct ptr *q;
};
struct node *start,*rear;
struct ptr
{
	char val;
	struct node *next;
};
struct node *create_new_node(int no,char pd1,char pd2)
{
	struct node *n=malloc(sizeof(struct node));
	struct ptr *temp=malloc(sizeof(struct ptr));
	n->x=no;
	n->p=temp;
	n->p->val=pd1;
	n->p->next=NULL;
	if(pd2!='$')
	{
		struct ptr *temp1=malloc(sizeof(struct ptr));
		n->q=temp1;
		n->q->val=pd2;
		n->q->next=NULL;
	}
	return n;
}
void insert(struct node *np,char op,int f)
{
	if(f==2)
	{
		if(start==NULL)
		{
			start=rear=np;
		}
		else
		{
			rear->p->next=np;
			rear=np;
		}
	}
	else if(f==1)
	{	
		rear->p->next=np;
		rear=np;
		start->q->next=rear;
		struct node *t;
		t=start;
		t=t->p->next;
		t=t->p->next;
		t->q->next=start->p->next;
	}
}
void display(struct node *np,char op)
{
	struct node *t=np;
	while(np!=NULL)
	{
			printf("%d on %c--->",np->x,np->p->val);
			np=np->p->next;
	}
	if(op=='*')
	{
		struct node *t1=t;
		printf("\nFor closure: -\n");
		printf("%d on %c --->",t->x,t->p->val);
		t=t->q->next;
		printf("%d",t->x);
		t1=t1->p->next;
		t1=t1->p->next;
		printf("\n%d on %c --->",t1->x,t1->p->val);
		t1=t1->q->next;
		printf("%d\n",t1->x);
	}
	else if(op=='+')
	{
		printf("\nFor addition:- \n");
		printf("%d on %c --->",t->x,t->q->val);
		t=t->q->next;
		while(t!=NULL)
		{
			printf("%d on %c--->",t->x,t->p->val);
			t=t->p->next;
		}
	}
}
void main()
{
	start=NULL;
	rear=NULL;
	char regex[100];
	int i,nodecount=0;
	printf("\nPlease Enter the regex:- ");
	scanf("%s",regex);	
	//printf("regex %s",regex); 
	for(i=0;regex[i]!='\0';i++)
	{
		if(regex[i]=='.')
		{
			struct node *np;
			np=create_new_node(++nodecount,regex[i-1],'$');
			insert(np,regex[i],2);
			np=create_new_node(++nodecount,'E','$');
			insert(np,regex[i],2);
			np=create_new_node(++nodecount,regex[i+1],'$');
			insert(np,regex[i],2);
			np=create_new_node(++nodecount,']','$');
			insert(np,regex[i],2);
			display(start,regex[i]);
			printf("\n");
		}
		else if(regex[i]=='*')
		{
			struct node *np;
			np=create_new_node(++nodecount,'E','E');
			insert(np,'*',2);
			np=create_new_node(++nodecount,regex[i-1],'$');
			insert(np,'*',2);
			np=create_new_node(++nodecount,'E','E');
			insert(np,'*',2);
			np=create_new_node(++nodecount,']','$');
			insert(np,'*',1);
			display(start,'*');
		}
		else if(regex[i]=='+')
		{
			struct node *np,*np1;
			np=create_new_node(++nodecount,'E','E');
			insert(np,'+',2);
			np=create_new_node(++nodecount,regex[i-1],'$');
			insert(np,'+',2);
			np=create_new_node(++nodecount,'E','$');
			insert(np,'+',2);
			np=create_new_node(++nodecount,']','$');
			insert(np,'+',2);
			np=create_new_node(++nodecount,regex[i+1],'$');
			start->q->next=np;
			np1=create_new_node(++nodecount,'E','$');
			np->p->next=np1;
			np1->p->next=rear;
			display(start,'+');
		}	
	}
}