Untitled

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
void main()
{
    char s[20],c;
    int state=0,i=0;
    printf("Enter a string:");
    scanf("%s",s);
    while(s[i]!="\0")
    {
        switch(state)
        {
            case 0: c=s[i++];
                if(c=='a')
	                state=1;
                else state=4;
            break;
            case 1: c=s[i++];
                if(c=='a')
	                state=1;
                else if(c=='b')
                    state=2;
                else state=4;
            break;
            case 2: c=s[i++];
                if(c=='b')
	                state=3;
                else state=4;
            break;
            case 3: if((c=s[i++])!='\0')
                state 4;
            break;  
            case 4:printf("\n %s the string is not recognized",s);
            exit(0);
        }
    }
if(state==1)
    printf("\n %s is accepted under the rule 'a'",s);
else if(state==2)
    printf("\n %s is accepted under the rule 'ab'",s);
else if(state==1)
    printf("\n %s is accepted under the rule 'abb'",s);
else
    printf("\n %s the is not recognized",s);
}