Implement (a/b)*abb using DFA

DFA

#include<stdio.h>
int main(){
  int i=0,state=0;
 char str[100];
   printf("\nEnter the string:- ");
   gets(str);
 while(str[i]!='\0'){
  switch(str[i]){
    case 'a':state=1;
     break;
    case 'b':if(state!=0)
    state=(state+1)%4;
     break;
    default:state=5;
     i=strlen(str)-1;
  }
  i++;
 }
 if(state==3)
  printf("\nValid String\n");
 else 
  printf("\nIn Valid String\n");
 return 0;
}