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Hello freinds,
Here I am posting my C implementation of DFA shown below. This DFA will accept any string containing 'a's and 'b' and last symbol should be 'a'.
#define TOTAL_STATES 2
#define FINAL_STATES 1
#define ALPHABET_CHARCTERS 2
#define UNKNOWN_SYMBOL_ERR 0
#define NOT_REACHED_FINAL_STATE 1
#define REACHED_FINAL_STATE 2
enum DFA_STATES{q0,q1};
enum input{a,b};
int Accepted_states[FINAL_STATES]={q1};
char alphabet[ALPHABET_CHARCTERS]={'a','b'};
int Transition_Table[TOTAL_STATES][ALPHABET_CHARCTERS];
int Current_state=q0;
void DefineDFA()
{
Transition_Table[q0][a] = q1;
Transition_Table[q0][b] = q0;
Transition_Table[q1][a] = q1;
Transition_Table[q1][b] = q0;
}
int DFA(char current_symbol)
{
int i,pos;
for(pos=0;pos<ALPHABET_CHARCTERS; pos++)
if(current_symbol==alphabet[pos])
break;//stops if any character other than a or b
if(pos==ALPHABET_CHARCTERS)
return UNKNOWN_SYMBOL_ERR;
for(i=0;i<FINAL_STATES;i++)
if((Current_state=Transition_Table[Current_state][pos])
==Accepted_states[i])
return REACHED_FINAL_STATE;
return NOT_REACHED_FINAL_STATE;
}
int main(void)
{
char current_symbol;
int result;
DefineDFA(); //Fill transition table
printf("Enter a string with 'a' s and 'b's:\n
Press Enter Key to stop\n");
while((current_symbol=getchar())!= '\n')
if((result= DFA(current_symbol))==UNKNOWN_SYMBOL_ERR)
break;
switch (result) {
case UNKNOWN_SYMBOL_ERR:printf("Unknown Symbol %c",
current_symbol);
break;
case NOT_REACHED_FINAL_STATE:printf("Not accepted"); break;
case REACHED_FINAL_STATE:printf("Accepted");break;
default: printf("Unknown Error");
}
printf("\n\n\n");
return 0;
}
